Second, given the simple galley style kitchens, I don't think it should cost too much since it'd be half a slab per kitchen without much custom work.

I’d say the easiest thing would be to create an LLC, not that expensive to do.

They back out of the contract, and now you have a half finished house with all their weird preferences that no one else wants.

If you aren't confident you can identify one, that's where you should be working.If you are, you should be working to get one under contract.Selling a good deal is the easiest thing in the world.

You dropped a half million on a place and then your parents decided not to move?

They would like to sell him half of the house while putting the whole loan under his name.

@Terrenze Walker,Finding buyers is probably the easiest part of the equation. 

It does have a newer roof and siding, 2 bedrooms, basement, kitchen, and 1 and half baths.

Also, if you have the cash and the deal is good enough, it might be worth it just to buy it with normal bank financing which is the easiest way to own it, with (usually) the lowest interest rate.  

This tends to be the easiest entry point into real estate for most people who don't have much saved up (and don't underestimate it's power!).