Ok I'm gonna throw it in here just becase...
You're going to be living with a "friend" AND his wife. Do yourself a favor, no matter how it runs NEVER and I mean NEVER, become involved with HIS wife. If you do you'll find yourself in a never ending spiral DOWN to the bottom.
Mike you seem to have a good head on your shoulders, I'm not discounting your age either (dumber things have been acomplished by more "mature" people in the past) but just a note. He has offered for you to live in his home, sharing the same 4 walls as him and his wife. Even if you pay them rent ALWAYS act as if you are a guest. Go get some groceries, buy the beer, take them out to dinner or slip them a gift card so they can have a nice quiet dinner together. Go on an over night trip once and a while so they can "be" with one another. Their's is a marriage, not a living situation so please respect that. Women are moody, irratable and demanding, of time, attention and $$$ .
Keep yourself in check, NEVER choose sides of an argument with them, if so you may begin to be her "shoulder to cry on" and that will end it with him, your bud.
Good luck and best wishes to you my man, if you really want to visit about the pitfalls of what happens to "friends" living in one home drop me a PM, no it's not about me just one of my best friends.
ds