Although when a car sits out in the desert sun too long the paint breaks down and surface rust forms on the outer surfaces. Mainly on the flat (horizontal) panels, but elsewhere as well. And while that isn't as damaging as cancerous rust in other areas, it is a lot of work to properly correct. Because like any rust it will come back through your new paint job, even if you sand it off. Rust has a way of living 'dormant' then coming back to life like a zombie. And having it over 60-70% of the car's exterior panels is a LOT to deal with. Plus being in the desert does not always mean no rust in the floors, rockers, etc. As you found all of the weather seals will deteriorate. And although it doesn't rain often, when it does it rains hard and all of that water goes directly into the inner cavities. Often owners of older cars here do not keep them protected from rain so it is not uncommon to find rusty floor pans, door bottoms, etc. Not to mention having EVERY soft material throughout the entire vehicle completely destroyed by the sun (not just the rubber seals). Take a close look at things like wire harnesses; you may find dried out insulation that has cracked, fallen off, and exposed the wires. And usually plan on replacing the ENTIRE interior, all the way to the bare metal surfaces. Engine seals, hoses, and other materials will be shot. And so on. Desert cars have their own set of problems that rivals rust belt cars in many ways.
