You thought you were long done with the day-to-day catering to your child's needs. When Junior flew the coop, it was supposed to be, well, for good. But after a rough patch in the adult world, he's suddenly back on your couch, his size 12s on your coffee table, planning another night out instead of a way out of your house.

Sigh ....

You may find some comfort in knowing that you're part of a growing trend of boomerang kids, and that the recession is much to blame for it. Multigeneration households have increased significantly over the past five years.

According to a survey by the Pew Research Center last December, three in 10 parents of adult children (29 percent) report that the economy forced their grown child to move back in with them in the past few years. Adults age 25 to 34 are among the most likely to be living in multigenerational households.

"A generation ago, living with your parents wouldn't have been accepted if you were an adult," says Christina Newberry, author of The Hands-On Guide to Surviving Adult Children Living at Home, a companion to her website. "The stigma is not there anymore."

Experts say that such living arrangements, frowned upon or not, can be a positive experience, but can also cause conflict if there's no proper planning. After all, taking care of an adult son or daughter could mean extra expenses at a time when you have your sights set on retirement. Or maybe you were hoping to downsize — and now those plans have been put on hold. And that thing you can't put a price on — your peace of mind — could take a hit, too.

So, should you get that desperate phone call from one of your own, lay down rules to help keep harmony in your relationship and to prevent your nest egg from dwindling.

Every expert we interviewed agreed that it's important to have a lease or some kind of written contract that sets out your expectations. Both parent and child should sign it, date it and file it for easy access. "You don't want to make [the stay] comfortable for them," says Deborah Owens, coauthor of A Purse of Your Own: The Easy Guide to Financial Security. "The fact that you allow them to come back home is a privilege."

Do what you can to help your adult child facilitate their own independence. — Photo by Alex Telfer/Getty Images

Here are eight rules to consider for that crucial document:

Rule No. 1. Your home is a "no freeloading zone." Make Junior pay a mutually agreed upon rent for room and board — this could be weekly, monthly or however you see fit. "Let them get into the habit of having a responsibility, which they will have when they become independent," Newberry says. "It's good for their self-esteem, too. It allows them to see that they are contributing."

Rule No. 2. Doing nothing is not an option. Hopefully, your child is earning some kind of outside income. But if you've got an unemployed college grad or a recently laid-off worker, delegate chores around the house, preferably the kind that will save you money. Painting the house, cleaning the gutters, cutting the lawn or helping you cross off a list of home renovations are all good options.

Next: 6 more rules you absolutely have to consider. »