I'd stay away from anywhere that uses a lot of salt. Mid west, upper mid west, North East US, are all suspect unless you can really look at the vehicle.
I was I the market for a full size SUV 18 months ago. A couple years old. Less than 50,000 miles. I had been looking at home (colorado), and found an Escalade in Iowa when I was there on a work trip. It fit the above criteria, was in my price range, went and looked. Interior was fantastic. Exterior looked good. Then I happened to check out the spare tire, and the entire underside was riddled with rust.
So, if you do consider it, make sure the seller sends you a lot of photos before you make the decision. And include the underside of the vehicle in the photos as well.