Rising rents have been cited as a reason millennials aren’t moving out of their parents’ basements. But higher rents could force some boomers to move in with their children.

So says Don Lawby, president of the Real Property Management franchise, a property management company based in Utah. He says it is shaping up to be a crisis for some boomers for the following reasons:

The average rent for a three-bedroom single-family home in the U.S. was $1,363 in the third quarter of 2015, a 5.7% increase over the last year, according to Real Property Management and Rent Range, a rental information company.

Workers 55 and over have, on average, saved only $150,300 for retirement, according to a Fidelity report from 2013. Assuming they withdraw 4% of their savings for income in retirement, their savings will generate about $500 a month, Lawby figured. With Social Security benefits, monthly income will average $1,791 (using figures from the Social Security website).

That monthly income means the average retiree is likely to have a housing budget of $609 to $681 a month (going by the recommendation that 34% to 38% of income be used toward housing costs), way below the cost of renting a three-bedroom home.

Rental growth rates are the highest they’ve been since the recession, said Ryan Severino, senior economist and director of research for Reis, Inc., a provider of commercial real estate information. Reis data shows that rents rose more than 4% over the last 12 months.

“Vacancies have been tight for a very long period of time,” Severino said. “That kind of environment gives landlords leverage to raise rents.” Rents are eventually expected to taper off, however, as more apartment inventory hits the market, he added.

Yet some don’t see that tapering off happening soon. A recent Rent.com survey of more than 500 property managers predicted rents would rise an average of 8% over the next year. Eighty-eight percent of property managers surveyed said they raised their rent in the last 12 months. The report also found that rental vacancies were at a 20-year low.

Steep rises in rent make it very difficult for tenants to keep up, “unless you’re in the job market and in a position where your salary is moving with the cost of living as it increases,” Lawby said. And he’s not just talking about retirees already living on fixed incomes. If you are a boomer who lost a job during the downturn, it is quite possible that your employment opportunities have been limited and salary increases have stalled, he added.

“The boomers, they’ve come into an environment that, generally speaking, hasn’t been positive financially for many of them,” Lawby said.

Owning is a safer bet

It’s important to point out that most retirees are homeowners, and therefore have more control over their housing costs — either because they own their home free and clear or have a fixed-rate mortgage that keeps their costs stable.

Of those between the ages of 55 and 59, 74.9% were homeowners in the second quarter, according to the U.S. Census Bureau. The homeownership rate was 80.7% for those between 70 and 74, and 76.8% for those older than 75.

And then there’s this: baby boomers now in their 50s have lower incomes, wealth, homeownership rates and more debt than generations before them, according to a report from the Harvard Joint Center for Housing Studies and the AARP Foundation. A third of Americans 50 and older spend more than 30% of their income on housing, while 37% of those 80 and older spend more than 30% on housing.

Certainly, the steep rise in rents is a reason why it is often safer for seniors to be homeowners, Severino said. You can bet that rents will go up over time, he added.

Yet there will always be some who rent in retirement, either by choice or need. And the jump in the cost of renting could force boomers with a lease to downsize from a three-bedroom to a studio — or maybe eventually move in with their kids, Lawby said.

“It’s something people should be thinking about before it becomes a necessity,” Lawby said, referring not only to the boomers, but their children who weren’t planning on taking in their parents.