In the game of real estate, this is what we call a full house.

Forty percent of millennials in America say that living within walking distance of their parents or in-law's is either "extremely or very important" to them, according to new research from the PulteGroup Home Index. So now, they're moving back.

South Florida real estate agent Brian Bahn, 32, is one of them. Bahn moved back to the city of Boca Raton, the suburban paradise where he grew up, after graduating from the University of Florida. He now lives within five miles of both his and his wife’s parents.

"I really think the cost of living has gone up so much, and for me in particular, it's the cost of childcare," Bahn, the father of a ten-month old girl, says. "It's made it much easier to build wealth and maintain our standard of living having our parents so close by.”

After his and his wife’s long workdays, “it’s a lot easier having my retired mom cook dinner for us than trying to get everything together ourselves,” he says. His family now spends “at least four nights a week” with either set of parents.

In addition to the ease of having parents nearby, living close to mom and dad makes financial sense for many young people. "In most markets, apartment rents have been rising faster than people's incomes. This is especially true for millennials," says Dr. Sam Chandan, associate dean of the New York University Schack Institute of Real Estate.

“With the deterioration of rental affordability in the United States, combined with the heavy student debt burden, moving home — and being able to save towards a down payment on a home — is a very attractive proposition,” Chandan, the host of Sirius XM Business Network’s The Real Estate Hour, adds.

Although this new research focuses on millennials moving closer to their parents (not back in with them), this trend often occurs in suburban areas, where costs of living may be lower than in big cities. Millennials, on the other hand, are often drawn to urban lifestyles, which can take a more significant bite out of any budget.

The question of jobs may also play into the desire to live closer to family. Previous research, like a study from the Federal Reserve Bank of Cleveland, has shown that proximity to parents can help laid-off employees bounce back financially.

[Living] near home, or with your parents, offers a kind of insurance in case you're laid off," wrote financial reporter Taylor Tepper in an article for Money.com earlier this year. "[Research] shows that parents can enlist their social network to help their progeny find new work, and might also motivate and encourage their kids to apply for another position that they may not have otherwise sought."

And still, experts point to other explanations, too. Boca Raton realtor Lisa Hindin of LANG Realty, a mother of two millennial-aged boys, believes that changes in parenting could play a role.

"Millennials today rely on their parents for more," Hindin says. "They take pride in family values ... and are closer knit. Especially where you see both [millennial] parents working, they really rely on their parents for childcare and support."

"It's about security," Hindin adds. "It's emotional and financial security, a safety net they really want." But, it's a two-way trend — Hindin has observed an uptick in the number of clients she's represented in recent years, who are middle-aged parents seeking to move closer to their millennial-aged kids.

Chandan expects this trend may increase in the years ahead — but partly tethers it to millennials’ growing interest in homeownership, a goal that can be accelerated by reducing expenses and living near one’s parents.

For people like Bahn, that's welcome news. But, does he have any words of caution for other millennials thinking to do the same?

"It's the emotional torture [of living near family]," he jokes, warning that having parents too close can mean regular badgering.

And, as a mother, Hindin agrees. "It's the nagging mother syndrome," she laughs. "Hence why my boys live so far away."