The garage that I am building now, and almost finished, was done a little different than what I have read here.
I guess it is T & M way. I did have to put down 10% up front of what the "Bid" was. But what it came down to, was pretty much at the end of every month or so, My builder would take a "Draw". He would summit EVERY SINGLE receipt up to that point for my review of the work that was done and all of the Subs paper work as well. He took 17% cut of what that total was on the bottom line, EXCEPT on his labor. His labor rate was just that and nothing else.
All of those numbers were put into a 6 page spead sheet, so you could see where all the money was being spent, AND that 10% that I put down, goes toward each draw. So if it was, say 20K, and you had 4 draws, then at each draw, 5K came off the bottom dollar.
There are not alot of builders out there that do it like this, but you can SEE where every single dollar is going. If you go over, you know where you went over, if you came under, you know where you can under.
I hope this makes sence to you