I fully agree with Rsporsch and jay . Rust that may have developed is surface rust. It won’t be as deep as you think. Furthermore there are products now available that after smooth sanding the whole car you can use to inhibit any bits of rust left (after sanding) on the surface. Your value of 20k for a freshly and completely painted running car is way low in my opinion as well. Personally it would be difficult for me to give up on the car. I am so sorry to hear about your car. Let me know if I can help anyway once you find the car... Best wishes! Tony P.