I have personal experience with that. When I was growing up my mother used to let homeless people (mostly older children like 17-19) stay at the house. While they were always nice to her, they would steal things from around the house and cash from my wallet. One day my Playstation was gone when I got back from school. One of them pawned it for drug money. It took a few bad incidents of that before she stopped letting homeless people stay. Unfortunately, it's too hard to trust people you don't know like that. My heart goes out to them and I would do what I could to help them, but letting them stay with you is a bad idea. I have seen first hand those situations get pretty messy.