I know that this is kind of off topic but here is my advice. A rusty, rotted car is a bit money pit. You are going to end up with a lot of time and labor and $$$ trying to bring it back from the dead. I would say that at least 50% of the time they never get finished because it is such a big project. And 90% of the time you are WAY upside down in it and you would have been much better off with a car in better condition.
I restored a rotted convertible only because it was an original 428 Cobra Jet car. Replaced pretty much every piece. This is a task beyond the backyard mechanic because you really, really have to know what you are doing to end up with a straight car where everything lines up. For example, when he put the floorpan and rockers in the door gap was noticeably wide at the top. I pointed that out and he said that once we got everything else on the car the weight would pull the body down and close the gap. He was right. And that expertise does not come cheap. I ended up with $20K in just the paint and body.