Understand the Situation
Before everyone gets too cozy, you need to initiate a conversation about your kid's plans and living arrangements. Make sure everyone understands the reasons why he or she is returning home. And, everyone should be involved in working toward the same goal, whether that's your adult child getting her own place after securing a job and a car, or just that she's using your love and comfort for a few months before moving out again.
You'll all feel better if you're on the same page with a definitive end goal in place.