I have to say you are the brave one...

yes I am a builder and I had done more than a few dozen of projects like it, but if I tell you it can be done under 30k, then I am lying to you.

structure framing is the hardest part of renovation, and it is really labor intensive, from the picture, roof system is custom build, house must build before truss was invented back in late 70s, to do it right and pass code, you may need to invest 10k just for that.

best luck to you and please post any update so we can all learn from you.