We're trying to build a low budget 6 window bus out. The bus was damn near free and is a little rust but we figured it would work for 3-5 years, after which we'll decide if we want something a little bigger.
I don't intend to keep an in-depth journal, but will post progress pics from time to time.
Here's some random pics:
Some underside rust(It's a Michigan bus):
Some more of the underside:
Some wheel well rust. I cut a large portion out. Along with what looked to be a 2 inch square tube that was rusted to hell. I plan on replacing the square tubing with new stuff, letting it sit on top of the frame rail. If I can figure out how. Then I'll patch over the top:

While a lot of the rust looks bad, and it is. I was surprised to find after cutting that chunk of the floor off, that most of it was still shiny under the rust, which gives me a little hope.
My girlfriend is going to grind down the rust and knock all the loose stuff free while I'm at work. Plan is to ospho the floor next week and weld it if I can find a respirator. I've checked every store in a 100 mile radius and they're all out.