From their first conversation, Nellie Goodwin knew that she and Sarah would make great roommates. For Nellie, 77 and recently widowed, Sarah’s sunny personality was a balm, and her weekend trips back to her parents’ house in the suburbs meant Nellie could still sometimes have the house to herself. For Sarah, who didn’t make a whole lot of money as a 25-year-old technical writer, the $600 Nellie charged for rent put pricey Cambridge, Massachusetts within reach.

The idea is that each age group benefits from the arrangement in a particular way.

At the very moment when many older people who are acutely susceptible to Covid-19 could use extra assistance, it has become risky for them to be in proximity to others, making intergenerational cohabitation a fraught prospect. A while back, Sarah moved to Alabama, where her fiance is getting his doctorate. Goodwin, who suffers from chronic health issues, is now on her own again. “I feel very isolated in a lot of ways, but I just can’t take the risk,” she says, “I’ve been getting requests [through Nesterly] from kids who are coming back to school in the Boston area and are looking for a place to live, but I’ve had to say I’m sorry, I can’t.”

For older people, sharing their home with a younger person can allow them to age in place, which has many benefits, from preserving long-standing relationships to preventing cognitive decline. Such arrangements have grown in popularity. Whereas just six years ago, only two percent of adults aged 50 and up shared or rented out a bedroom or “accessory dwelling unit” in their homes, today 16 percent do.

There are about 60 senior/youth homeshare programs in the U.S. Some are decades old, others less than a year. There are independent free-market connectors, and government-sponsored programs to serve senior citizens. A few have become international platforms in the style of Airbnb, like Homeshare UK, which started in the late 1980s in London and has now expanded to 16 other countries. For young people who have grown up immersed in the “sharing economy,” services like Nesterly solve a housing problem the same way Uber solves a transportation problem or WeWork solves an office space problem.

According to the AARP’s research, older people’s reasons for sharing their home with a stranger tended to be practical: 58 percent wanted the renter to help with everyday activities, 50 percent did not want to live alone any longer and 49 percent wanted the extra income. Perhaps more important, about 75 percent wanted to stay in their current residence as long as possible.

Read more in Reasons to be Cheerful.