Rust Removal and painting.

Rust is one of those things where for every bit you see, there's usually twice as much more hiding. Personally I wouldn't even try to fix a rusty car unless it was a rare classic, but then rust is relatively rare here and completely rust-free 80s Volvos are not hard to find. The best option depends on the amount of rust damage, surface rust can be sanded off and filled, rust holes need to be cut out with new metal welded in. For paint, you get what you pay for. You can improve a Maaco job significantly by doing all the tedious prep work yourself, but you're still looking at a couple thousand dollars for a decent paint job that's anywhere near what the car originally came with.