This is my situation only, but it may help. I work for a custom home builder and handle his financial stuff, and his contracts work on a pay-as-you-go. Sort of. Usually, a mortgage is involved, so the bank is handing out the dough. After the foundation is complete, he applies to the bank for his first 20% draw. They come out and verify that the foundation is actually done, and give him his money. Then when the framing is done, same thing. And so it goes. For a typical family, they will have sold their souls to the bank at this point, so for them it’s not pay as you go.
However, he is currently building a house for Mr. Stuff and me. We are paying cash, so things are slightly different. Same schedule, but we cut a personal check instead of going through the bank. Under these conditions, if we ran out of money, the house could indeed be abandoned. Barring unforeseen major events, it won’t be, but theoretically, it could happen.
Also, I don’t know if you got a look inside the houses that were nearly finished to your eye. After a house is framed, a great deal goes on inside that makes up a lot of the cost. For instance, was the drywall done? The electrical? The plumbing? On a $200K house, those three things can run you $33K or more. None of them are visible from the outside, so a significant part of the house can be undone while looking as if it’s nearly ready to move into, after some siding has been added. (I forgot to mention the kitchen cabinets, which by themselves can be $15K.) As always, YMMV.