Ditto what Down2sea posted. I bought a car to restore for my wife and though I am still in the beginning stages, I've already spent nearly as much on parts as I originally estimated (there were a couple of problems I found during tear down that I didn't see prior to purchase). I still haven't gotten into the AC system to see what I can salvage. So, I would say estimate the cost like Down2Sea says and then double it just to be safe.
