Here's a solution that could tackle two of the West's most urgent problems: a young generation priced out of affordable housing, and the loneliness and isolation of a rapidly ageing population.

For so-called millennials, like Mikyoung Ahn, a large home is a seemingly unattainable dream. She could not imagine living in a spacious detached house on the leafy outskirts of Paris, just half an hour from the Arc de Triomphe. She definitely couldn't imagine paying just 120 Euros (£100) a month to live there.

Yet, with the help of an innovative housing scheme, that idea is no longer a fantasy for the 25-year-old student from Seoul, South Korea.

An aspiring architect, she wanted to live and study in one of the world's cultural capitals. To realise her dream, she turned away from traditional student accommodation. Instead of moving in with other young people, Mikyoung chose as a landlady and housemate a 78-year-old widow with a passion for patchwork.

"I knew I was going away from home for university, and that I wouldn't have any family or any friends," she says. "But after the first meeting her, I knew it was going to be perfect."

Mikyoung and her landlady, Monique, have been living together since October, after they were matched by an organisation called Ensemble2Generations. This organisation and others like it pair elderly people with students, in an arrangement called homeshare.

The concept is simple, yet it attempts to bridge an intergenerational divide that exists in many parts of the world.

On one side are older people, who own properties that were purchased when house prices were comparatively cheap, but who may now need some help with daily activities like shopping and cleaning.

On the other side are young people, who cannot afford to rent a decent flat, but who may have some time to spare.

Image caption Monique has got Mikyoung into her hobby, quilting

Mikyoung helps Monique with a range of everyday tasks. She carries Monique's shopping in the supermarket, washes up, and has even created an instruction sheet to help Monique understand all the buttons on her TV remote.

"It's not a big deal," she says. "It's just life, you know. If I lived here, I would have to clean the dishes or take the trash out. I feel really this is my home - this is our home.

"Every night when I come back, I prepare the dinner and I put on the music that I have learned today. For example, Champs-Élysées or something like that, and we sing together."

Monique, who is a retired schoolteacher, is now an avid fan of Downton Abbey, after being introduced to the programme by Mikyoung.

"We have very good moments together, because we share a lot," says Monique. "We often sit together and watch TV programmes. Everything is simple between us."

Turning to Monique, she adds: "You are like a granddaughter to me."

Homeshare is not a new idea - it was first trialled in the USA and Spain during the 1980s. However, experts have recently started to view it as a scalable solution to two problems that continue to cause social problems. While young people are migrating to cities, pushing up the price of rent, many populations in the developed world are ageing.

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Homeshare schemes are now active in 16 countries across the world. Since 1999, an organisation called Homeshare International has acted as a network for homeshare schemes.

"The benefits to the householder are they feel much safer at home because of having someone else in the house," says Elizabeth Mills, the organisation's director. "They're happier, incidents of accidents and falls go down, and the reassurance for the householder's family is absolutely enormous."

Most programmes offer two homeshare arrangements for prospective participants. The first allows the student to live in an elderly person's home rent-free in exchange for help around the house. The second requires the student to contribute money to household bills, but places fewer burdens on their time.

Image copyright Getty Images Image caption It costs roughly 900 Euros a month for a student to live in the centre of Paris

So will schemes like this help solve the housing crises of millenials - and the problems of the elderly?

Research into homeshare projects in Spain and the USA indicates that participants are overwhelmingly satisfied by the arrangement. The Spanish study, for example, reported that 93.2% of elderly people had benefitted in some way from the programme, while 98.7% of students had benefitted.

The organisation that paired Monique and Mikyoung, Ensemble2Generations, conducts face-to-face interviews before placing people together. Students even have to put pen to paper to explain why they want a placement, so that their application can be examined by a handwriting expert. Despite this, some partnerships simply do not work out.

She's like a companion. It's so good to have a presence in the house Armelle, Homesharer

A major issue is that people of different generations may not always get on. Monique's previous housemate was a young gardener who spent a lot of time out of the house. When they did occasionally eat together, the gardener did not want to have a conversation. Instead, according to Monique, he just stared vacantly at his phone. But that did not shake Monique's confidence in homeshare.

"I never doubted whether I wanted to homeshare. I knew there were other people out there… It is a good solution for me."

And although the gardener did not provide much companionship for Monique, experts widely acknowledge that homeshare is an effective antidote to loneliness - a problem that affects over one million elderly people in Britain, according to Age UK. Helen Bown, a policy expert who specialises in social isolation, says that the emotional support provided by a homeshare relationship often exceeds its financial advantages.

"People talk about not feeling so lonely anymore, particularly people who are single, " she says. "People have talked about having a safety net, particularly at night.

"I think one of the most compelling things that people have talked about, consistently, is the impact emotionally for people - the positive relationship. The feeling that people are contributing; that they are part of a mutually beneficial relationship, not just a transaction of care and support."

This is certainly the case for Armelle, a 64 year-old woman living in Cergy, northwest of Paris. Eighteen months ago, Armelle's husband died of cancer. Devastated, and fearing loneliness, she got in touch with Ensemble2Generations. Since then, she has housed a 19-year-old student called Blandine, from Versailles, who is studying engineering at a local university.

"If my husband had been here, I would never have thought of accommodating a student," says Armelle. "But she's like a companion. It's so good to have a presence in the house. I enjoy Blandine's company a lot."

Image caption Armelle and Blandine have an easygoing friendship

Armelle and Blandine's relationship is like a casual friendship. They relax together in the evenings and chat about their lives. While she was away from the house for a few days, Armelle even allowed Blandine to have a house party.

"Though her contract says that she's not allowed to have friends over, I know that I can trust her," says Armelle, laughing. "I even helped her organise it."

The house has a large fireplace and a spectacular view over the lakes of Cergy. Unsurprisingly, Blandine is fond of these home comforts, and is not keen on moving into a cramped student flat for the next academic year.

"In student accommodation everything is in the same room, except for the bathroom," she says, wrinkling up her nose.

"I have a few friends who are offering to flat-share next year. I tell them, "Why not?" but I'm actually very comfortable here - I'm not sure I'm going to leave."

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