Aver, I don't think you should feel guilty about the house at all. It's something YOU made happen as well as H. As LFA says, he's the one who walked away from it, not you.
Look on the bright side, if he's offering $64K & you were expecting $100K then you're $36K better off than you started off thinking.
There's no reason you can't buy him out, then either rent out the house, keep the room mate or sell it and get the low maint bungalow when the market picks up.
The thing is it will be YOUR choice Aver, that gives you a HUGE amount of freedom to do what you want.
H: 44 W: 42 Married: 23 years Bomb: 16/07/2009 PA Confirmed: 16/01/2010 Over it & working on ME: Feb'ish 2010