The numbers support this option. Since 2017, nearly half of renters have spent 30 percent or more of their incomes on housing costs, which is an unsustainable portion, according to the U.S. Department of Housing and Urban Development.

At the same time, an astounding 54 million spare bedrooms sit empty every night. Many of these spare bedrooms are located in the homes of older Americans, with millions more expected over the coming years.

The National Shared Housing Resource Center lists about 40 formal, non-profit, home-sharing services in the United States, such as Odd Couples Housing in St. Louis, which mostly matches students with older adults, and Home Match San Francisco, which has attracted young working professionals and students who can't afford the city's steep rents.

The benefits of age-integrated housing are tangible and wide ranging. By opening their homes, older adults can gain monthly income and household support (such as grocery shopping, dog walking or meal preparation) in exchange for lower rent and even a new friendship.

"I feel comfort coming back at night to a home with lights on," said Brenda Atchison, an empty nester in her late 60s who in recent years has rented rooms in her Boston home to several young people.

"While no one approach can perfectly solve the challenges presented by the confluence of a rapidly aging society and the housing crisis, intergenerational home-sharing models offer communities an innovative, flexible way forward," according to Marcus.

"With an astute approach to scaling and reverent use of technology, home-sharing can help young people access affordable housing near jobs and opportunities, and ensure that our parents and grandparents age with choice and dignity. Indeed, it can help create a world where housing security isn't just for the privileged, it's for everyone."