Yes, you are right. He would probably help if we sold before D. I'll still have to keep the house prepped for showings (not easy with a little one!), and deal with coordinating that, etc. Maybe I will put some $ value on that time/effort in our agreement...
I think my point was that if I just buy him out before D, he gets all his equity out without having to put in any time, effort or $ to sell it. I suppose that could be negotiated too, IF I could get a mortgage and really wanted to stay here.