Coping with boomerang kids

Despite your—and your child's—best efforts, there might come a time when it makes sense for an adult child to return home for a while. A newly married couple might move back in to save money before buying their own home, for example. Or a kid who has been away at college might come back to save for graduate school.

Whatever the reason, experts say it's a good idea to agree in advance on the appropriate end point—such as buying the home or going off to grad school in the above examples. Clark likens this to a basic principle of psychology that you may remember from your own time in college. "If a lab rat knows that he can push a button to get a piece of cheese, he'll never go anywhere else to eat," he says. "Every child should know home is a safe place they can return to when they really need it. But don't let them get too comfortable."