That happened to me and my mom let me move back in. I know she would let my brother or sister move back in if they ever needed it. But it also depends on the child. If you think your son is the type that will take advantage of you then there has to be boundaries like "you can move back in but you are paying rent and only allowed to stay x amount of time" but I think most 25 yr old men wouldn't want to live with their parents unless absolutely necessary. I worked overtime while going to school full time just so I didn't have to live with my parents. I think that's the point that pride moves in and hopefully he would want to move out as soon as possible. But thats the role of parents. Let your kids make mistakes and be there to help pick up the pieces if/when they fall flat on their faces.