And seniors, who might otherwise feel isolated as they try to keep up with bills and daily household tasks, get a little boost from their housemates.

Such a strategy could serve as a backup retirement plan for older homeowners whose retirement savings hasn’t quite come up to the mark. They can offer a housemate a place to live at what, to a millennial, is a reasonable price, while the younger person can offer the elder help with anything from laundry to cooking.

This can be particularly helpful if the senior in question has found him- or herself retiring earlier than expected, whether through downsizing or health problems, and the extra money may help to offset a premature retirement—or, at the very least, provide assistance with some household duties that may over the years have become a challenge.

While many homesharing arrangements require payment at varying levels, depending on the needs of each, others may be strictly on an in-kind basis; in the former, the younger person pays a reasonable rent and provides help with shopping, cleaning or some other task, while in the latter, no money changes hands but daily chores get done without the older person having to do them or hire help.

Boomers are increasingly coming up short on money in the wake of the Great Recession, which devoured many people’s retirement savings, and many try to hide the fact from the world even as they search in a job market that’s not what it used to be and struggle with the fact that after years in the workplace making a good salary, they’re broke—or close to it—and if they do find a job, it may not have benefits.

As workers age, they’re downwardly mobile; the older they get, the lower the salaries offered.

A homeshare arrangement can mean the difference between subsisting on whatever’s on sale and doing without medication or paying the bills late, and being able to keep current with essentials.

There are more intangible benefits, such as companionship. Many seniors suffer ill health and higher stress from being alone and not being part of a community. However, if housemates get on well together, the elder might find that having someone to share interests with can result in health benefits as well as better morale.

And lest you think the young don’t get all that much out of the arrangement, consider this: the housing market has been roaring again, which means that home purchase is out of reach of many millennials and even an apartment to rent—solo—could be out of the question.

In fact, according to a Realtor.com report that evaluated the nation’s 150 biggest markets to see how many homes out of each market’s total housing stock are actually available for sale, the market is so tight in many places that there’s barely anything available.

Among those places is Seattle, Washington, where only 0.4 percent of the city’s housing stock is for sale after shrinking by 13.4 percent last year; Eugene, Oregon, where only 0.6 percent is available after shrinking by 27.3 percent last year; and Buffalo, New York, with 0.6 percent available after a 2016 tightening of 15.9 percent.

Homesharing may not be the answer to everyone’s problems, but it certainly offers some opportunities to both boomers and millennials.