I read most of this thread at work today but then the new guy who makes my office space his own was being nosey. I wouldnt log in because then I would be revealed. But I wanted to say this if no one has said it yet. Allow yourself to be used (financially that is) and use him financially.
In some instances it is good to follow a man's lead. When they give you give when they hold back you do the same, when they take you take. If you are going to be living there helping him to pay the interest so he can get to his equity quickly then allow the money you save by not paying for your own place along with utilities and $ave! $ave! $ave!
Basically, if you would have been paying $700-800 for your own place (this includes total) then with him if you are paying $500 and put that extra $200 away in the bank. Set a goal for yourself, should you not be married, on the deed and mortgage as you wish. Buy your own place and move out then send him a thank you card.
Also, you have to think in this day in age, things happen, the last thing you want to do is be tied through credit only with a man who could possibly become disabled or lose his dream job and have him become inefficient for an amount of time meanwhile ticking you off with his unattractive pity-party attitude and putting the majority of the financial problems on you esp. the mortgage which you will be responsible for credit-wise.
I say don't get involve legally, but if what bob says it's true benefit from your investment because you know he will. Also, stand firm on what you are willing to pay else you would not be able to save. And don't let him know you have saved, I don't care if his car breaks down or he needs special shoes, teeth or hair.
In any event I wish you the best, I so could not be in that position. I am far too selfish with success to be outselfished. When I work hard towards something it's gonna be for my benefit majority or all. I was born in the world alone, I will walk my path the same way.
Should I meet someone along the way, he or she will still need their own water canister. And even if they have more water than me, I will hold off on drinking mine throughout the sunny heat wave until they have the same amount as me or I have more.