Oddly enough, I tried this experiment last winter. It was very intertaining having up to a dozen former homeless in my 1000 sq ft house, garage and basement.
They are out now, although occaisonally one will drop by and thank me for helping them, and just to say hi. Mostly they were good kids, in trouble. Having a warm place to sleep, and address to put on an employment application and access to a shower and laundry facilities was the leg up they needed.
Mostly they respected my room and personal property. I did lose some minor stuff, but I think on the whole I made a positive difference in some of their young lives. And mine.
I really appreciate my own good fortune, having seen so many examples of how bad it could have been.
That being said, there are REAL REASONS some of them were homeless...