My gut instinct says he will 
this up. He has not been able to hold it together and do what he needs to turn his life around and especially with the girls he has been meeting and keeping time with, I don't think it's a good idea for you to get this involved. It's just my opinion and I know it's what you need to do to sleep at night, but history has proven that he is not ready for this responsibility.
Just my opinion and I really hope it's wrong. I would probably be doing the same thing in your situation, though I would also know what I was doing was wrong. What happens when he doesn't pay the rent? Will you then be liable to do so?? It's not going to be an easy situation since this is a friend of boyfriend.
