Adult children moving home
It's one thing when your child, even one who has graduated from college, has decided that continuing to live with you (the parents) rather than on their own has many distinct advantage. It's quite another when they have been on their own and now decide it's necessary or time to move back in with you.
Not only have you adjusted to them being gone, but they are used to living life as they see fit and this may no longer mesh with your ideas of how life should be lived. Can you say no? Sure, but you probably won't. After all, they probably have good reasons to move back home. What is important is that ground rules are set in writing, timelines for accomplishing various goals are clearly defined, and both parties agree. Then and only then should you take them back.
Although you may initially love having them back home, be prepared for daily frustrations. Don't let them have their way, and don't let them become too comfortable. Remember that the goal is short-term assistance, not a long-term lifestyle change.