There is a company (US Car Tool) that advertises here about a body in white program. For 18K they will get the body straight with all needed patch/replacement panels.
http://uscartool.com/body-in-white/
There has been a bunch of threads on this, but unless you can find a good, quick, reliable and cheap body guy, this is probably a very good indication of the cost of doing a full rust repair job.
There are other threads on how rare a good, quick, reliable and cheap body guy is too. As soon as cheap gets into the mix, you usually lose at least 1 or 2 of the other 3 qualities.