Eva, a 19-year-old student at Nairobi Aviation College, was sitting in her tiny room in shared quarters in Kitengela feeling broke, hungry, and desperate. She used the remaining 100 Kenyan shillings she had in her wallet and took a bus to the city centre, where she looked for the first man who would pay to have sex with her. After 10 minutes in a dingy alley, Eva went back to Kitengela with 1,000 Kenyan shillings to feed herself for the rest of the month.

Six years ago, when she was at university, Shiro met a married man nearly 40 years her senior. At first, she received just groceries. Then it was trips to the salon. Two years into their relationship, the man moved her into a new apartment because he wanted her to be more comfortable. Another two years down the line, he gave Shiro a plot of land in Nyeri county as a show of commitment. In exchange, he gets to sleep with Shiro whenever he feels like it.

Eva's experience is transactional sex in its most unvarnished form - a hurried one-off encounter, driven by desperation. Shiro's story illustrates an altogether more complex phenomenon - the exchange of youth and beauty for long-term financial gain, motivated not by hunger but by aspiration, glamorised by social media stars, and often wrapped in the trappings of a relationship.

Older men have always used gifts, status, and influence to buy access to young women. The sugar daddy has probably been around, in every society, for as long as the prostitute. So you might ask: "Why even have a conversation about transactional sex in Africa?"

The answer is that in Kenya, and in some other African countries, "sugar" relationships seem to have become both more common and more visible: what once was hidden is now out in the open - on campuses, in bars, and all over Instagram.

Exactly when this happened is hard to say. It could've been in 2007 when Kim Kardashian's infamous sex tape was leaked, or a little later when Facebook and Instagram took over the world, or perhaps when 3G internet hit Africa's mobile phones.

But somehow, we have arrived at a point where having a "sponsor" or a "blesser" - the terms that millennials usually apply to their benefactors - has for many young people become an accepted, and even a glamorous lifestyle choice.

You only have to visit the student districts of Nairobi, one recent graduate told the BBC, to see how pervasive the sponsor culture has become. "On a Friday night just go sit outside Box House [student hostel] and the see what kind of cars drive by - drivers of ministers, and politicians sent to pick up young girls," says Silas Nyanchwani, who studied at the University of Nairobi.

Until recently there was no data to indicate how many young Kenyan women are involved in sugar relationships. But this year the Busara Centre for Behavioural Economics conducted a study for BBC Africa in which they questioned 252 female university students between the ages of 18 and 24. They found that approximately 20% of the young women who participated in the research has or has had a "sponsor."

The sample size was small and the study was not fully randomised, so the results only give an indication of the possible numbers, they cannot be taken as definitive. Also, only a small percentage openly admitted to having a sugar daddy; the researchers were able to infer that a number were hiding the truth from answers they gave to other questions, using a technique called list randomisation. But interestingly, when talking about others, not about themselves, the young women estimated on average that 24% of their peers had engaged in a transactional sexual relationship with an older man - a figure very close to that reached by the researchers.

Jane, a 20-year-old Kenyan undergraduate who readily admits to having two sponsors, sees nothing shameful in such relationships - they are just part of the everyday hustle that it takes to survive in Nairobi, she says.

She also insists that her relationships with Tom and Jeff, both married, involve friendship and intimacy as well as financial exchange.

"They help you sometimes, but it's not always about sex. It's like they just want company, they want someone to talk to," she says.

She says that her religious parents brought her up with traditional values, but she has made her own choices. One of her motives, she says, is to be able to support her younger sisters, so they won't need to rely on men for money. But she has also been inspired by Kenya's celebrity "socialites" - women who have transformed sex appeal into wealth, becoming stars of social media.

Among them are the stars of the reality TV show Nairobi Diaries, Kenya's own blend of Keeping up with the Kardashians and The Real Housewives of Atlanta. The show has launched several socialites out of Nairobi's slums and on to yachts off the coast of Malibu or the Mediterranean.

"Nairobi Diaries is like the Kardashians playing out [on screen] in real time. If I look hot, I look good, there has got be some rich guy who will pay good money to possess me," says Oyunga Pala, Nairobi columnist and social commentator.

The best known of the Kenyan socialites is probably Vera Sidika, who went from dancing in music videos on to the set of the Nairobi Diaries, and from there launched a business career based on her fame and her physique.

"My body is my business - and it is a money maker," she said back in 2014, when discussing her controversial skin-lightening procedures. Nowadays, Vera is keen to promote herself as an entrepreneur, and runs a successful brand of "detox" herbal infusions called Veetox Tea.

Equally famous is model and socialite Huddah Monroe, who also rose to fame on reality TV - in her case Big Brother Africa, in 2013 - and who now runs a well-established line of cosmetics. "If you have to expose your body, make money out of it," she was reported as saying, referring to the semi-nude images that she shows off to her 1.3 million Instagram followers.

In the past, some of Kenya's socialites have styled themselves as #SlayQueens, and have been quite upfront about the financial benefits that have come from dating tycoons. Having made it to the top, though, they often begin to cultivate a different image - presenting themselves as independent, self-made businesswomen and encouraging Kenyan girls to work hard and stay in school.

The millions of fans scrolling through their Instagram posts, though, are not blind. The sudden emphasis on entrepreneurship does not hide the fact that these women used their sex appeal to create opportunities in the first place. And many - quite understandably - are attempting to apply this methodology to their own lives.

One of those who has succeeded is Bridget Achieng, a woman from the sprawling Nairobi slum of Kibera, who worked as a domestic servant - a house girl - but who gained a social media following on the back of a sexy photoshoot, and then found her way on to the cast of Nairobi Diaries.

Her message to aspiring socialites, though, is that nothing is free. "You want a million bucks, you will do something that is worth a million bucks."

If one end of the sugar spectrum features young women with their sights set on a hot pink Range Rover, a luxury condo and first-class tickets to Dubai, at the other are women angling for little more than some mobile phone credit and maybe a lunch at Java coffee house.

But the gulf between them may not be so deep as it seems.

"Should I leave all these Gucci Prada? Na which young girl no dey fear hunger?" sang the Ghanaian singer Ebony Reigns, encapsulating the mixture of social aspiration and economic anxiety that many young women feel. The desire not to go hungry and the desire to taste the good life can easily run side by side. And the fortunes of a woman dependent on a sponsor can change in an instant - either for better or worse.

Grace, a 25-year-old single mum from northern Nairobi, has a regular sponsor, but is actively seeking a more lucrative relationship with a man who will invest in her career as a singer.

She is poor by the standards of middle-class Kenyans, often living hand-to-mouth, dancing for cash in a nightclub, and struggling to put her daughter through school. But her determination to feed and educate her child coexists with a naked ambition to become rich and famous through modelling and music.

"I need to be a star," she says, citing not just Vera Sidika but also Beyoncé. Is she driven more by vanity or poverty, aspiration or desperation? The lines are blurred.

Both Grace and Jane have come of age in the last decade, bombarded since childhood with images of female status built on sex appeal. But according to Crystal Simeoni, an expert on gender and economic policy, Kenyan society encourages sugar relationships in other ways too.

If women have become more willing to profit financially from their youth and beauty, she says, it's partly because of Kenya's gross economic inequalities, lack of social mobility, and widespread corruption.

"The way things are constructed in this country makes it so much harder for a smaller person to make ends meet," she argues. Hard work won't get them anywhere. "They have to get a sponsor, rob a bank, or win a tender."

Michael Soi, a well-known artist whose paintings satirise Kenya's culture of transactional sex, takes a similar but more cynical view, attributing the phenomenon more to laziness and a get-rich-quick mentality than to structural injustice.

The days of waking up early and working from morning to night are behind us, he says: "Right now the ass is the new brain, and this is what you use to get what you want."

The phenomenon isn't confined to women.

George Paul Meiu, who studies transactional relationships between men of Kenya's Samburu tribe and older European women, has described how their youth and good looks have become valuable commodities in Kenya's beach resorts.

Thanks to a set of "African warrior" stereotypes and myths about tribal sexual prowess, the Samburu and others like them are particularly appealing to both local and foreign sugar mummies. Some Samburu villages, he says, claim they have been unable to defend themselves against cattle raids from neighbouring tribes because so many young men have migrated to the coast to become beach boys.

"A beach boy is someone who gets up in the morning, smokes a joint, lies under a coconut tree waiting for bikini-clad white woman passing on the beach and runs after them," says artist Michael Soi.

But as most of those dependent on sugar relationships are female, they have dominated the public debate. There are concerns about the morality of their lifestyle, but also about its consequences for their health.

Kerubo, a 27-year-old from Kisii in Western Kenya, maintains that she has control of her relationship with her sugar daddy, Alfred. But when I ask her about safe sex, this illusion quickly evaporates.

Both Alfred and her other sponsor, James, prefer not to use condoms, she says. In fact she has had unprotected sex with multiple sugar daddies, who then have sex with other women, as well as with their wives, exposing all of these partners to the risk of sexually transmitted diseases.

Dr Joyce Wamoyi from the National Institute for Medical Research in Tanzania says girls and young women between the ages of 15 and 24 have consistently been at higher risk of HIV infection than any other section of the population in sub-Saharan Africa.

Sugar relationships, she says, are contributing to these risks because the women who engage in them do not have the power to insist on the use of condoms. "With sex work, men are more likely to use condoms because it's more explicit that this is selling and buying."

A look at the Kenyan tabloids also suggests that women are at risk of violence from their sponsors.

It's not hard to find headlines such as "Stabbed to death by a man who has been funding her university education," "Kenyan 'sponsor' threatens lover, posts COFFINS on Facebook and she DIES afterwards," "Pretty 22-Year-Old Girl Killed By Her Sugar Daddy." These articles all describe, sometimes in graphic detail, sugar relationships that led to murder.

Jackie Phamotse, a South African businesswoman who survived an abusive relationship with a "blesser", described her experiences in a tell-all book, Bare: The Blesser's Game.

Most young women, she says, are not aware of the dangers. "Some of the girls who disappear around our continent were in these transactional relationships… Looking at the police reports, these are cases of girls who were in relationships with older people, and they were rejected at some point and someone decided to kill them."

Phamotse eventually fled her abuser, with nothing to show for the relationship. "I had to escape so I didn't find any financial privilege," she says. "I left the house and the car, and had to rebuild my life."

No-one really knows how many sugar relationships end in sexual abuse or physical harm. Kenyan academics and NGOs have made extensive studies of domestic violence, and of the risks faced by sex workers. But on the subject of transactional sex there is no research - only the lurid anecdotes of the tabloids.

Among Kenyan feminists, the rise of sponsor culture has provoked intense debate. Does the breaking of old taboos around sex represent a form of female empowerment? Or is sponsor culture just another way in which the female body can be auctioned for the pleasure of men?

"There has been a rising growth of the women's movement in Africa and a rising feminist consciousness," says Oyunga Pala, the Nairobi columnist. "Women who were vilified for being sexually active have been given license to just be. There is less slut-shaming than before."

But while some feminists argue that any choice a woman makes is inherently feminist - because it was made by a woman - others question how free the choice to enter a sponsor relationship really is.

"A feminist approach to freedom of expression, even with sex work and prostitution, is a northern perspective that says you should be allowed to do what you want to do," says Crystal Simeoni. "But that is coming from a point of privilege. A lot of times these women don't have a choice - it's life or death."

Mildred Ngesa, an ambassador for the global activist group Female Wave of Change, makes a similar argument. After decades of women struggling for the right to vote, to own land, to go to school, she argues, the "choice" to engage in sugar relationships is steeped in contradiction.

"If we say it's her right to be a prostitute, we are sending her right back into the jaws of patriarchy."

But is it prostitution, or something different in subtle but important ways?

Jane, the student, makes a distinction, arguing that "in these relationships, things are done on your terms", and Dr Kirsten Stoebenau, a social scientist who has researched transactional sex in Kenya, agrees that this is significant.

"It only becomes sex work when the woman engaging in these relationships describes her sexual partners as clients, when she describes herself as engaged in the sexual economy and when the encounter and exchange is pre-negotiated, explicit, usually immediately remunerated, and often devoid of any emotional connection," she says.

Grace, the aspiring singer struggling to put food on the table, has a slightly different perspective - to her the similarities with sex work are more apparent.

"I prefer the sponsor thing, rather than standing on the street," she says. "Because you have that one person who is supporting you… you don't need to sleep with so many men."

The artist Michael Soi notes that Kenya remains on the surface a religious society with traditional sexual mores - but only on the surface. Those who deplore sex before marriage and infidelity within marriage rarely practise what they preach, he argues, and the condemnation of sugar relationships is tainted by the same hypocrisy.

"We're constantly bombarded with moral ethics, and with what religion does and doesn't allow. But it's all a pretence," he says. "We're just burying our heads in the sand and pretending these things don't happen."

For many young Kenyans, the values espoused in families, schools, and churches simply do not align with the economic realities of the country, or cannot compete with the material temptations that, in the age of reality TV and social media, are everywhere visible.

Even within the family, most Kenyan girls have it drummed into them from an early age that they must marry a rich man, not a poor one. It's taken for granted in these conversations that men will provide the money on which women will survive. So for some it's only a small step to visualising the same transaction outside marriage.

"What is wrong about sex anyway?" asks Jane. "People just make it sound wrong. But sometimes, it ain't wrong at all."

Some names have been changed.

Nyasha Kadandara is a Zimbabwean journalist and film-maker who works mostly in sub-Saharan Africa.