Well I made it through the drama here and really I must say I'm impressed by the wealth of common sense and wisdom that has been expressed here. I had begun to despair that my views were so out of touch and old fashioned, but really it seems to me that most people have counseled against the OP helping his "friend" in his time of need. We must realize, though, that the OP is only in his 40's and may still inexplicably retain some mis-placed belief in the basic innocence and decency of humankind and that his friend - with the drinking problem as well as impulse control issues, to say nothing of his apparent estrangement with his family (always a good card to play in these games), will always remain the sweet pliable young man who has lived off his looks and youth and will of course move out at the first whiff of discord. Yeah, right.
I plan to keep my eye on this evolving dramedy and I'm laying in plenty of popcorn to eat while the saga unfolds. My advice to the OP is to start a journal and write down all the events as they unfold - I think you'll have a good story here, worthy of An American Story or some such horror.
Remember also that even if the new live-in decides to go to court to enforce whatever legal rights he may or may not have, you will also have to go to court with legal representation. Yes, yes, you may be entitled to get your court costs paid by the live-in, but remember there is such a thing as a judgement-proof defendant. If he already has money issues and job issues, how likely is it that you will come out of this debacle with no scars to show for your supposed virtuous intentions?