There is no best geographic location for problems on a used car. The only issues that come up are rust and paint issues on a car as you mentioned. In colder areas where they use salt and other antislip coatings on the roads come winter time is where you might have to be concerned. Buying cars from desert states, the bodies will be in better condition. Mechanically will they be better than other areas? Maybe not. I bought my car local because I didn't want to ship it or drive out. I found a clean example within 10miles of my home.