I have bought a few old but desirable cars from AZ (one stepdaughter lives in Phoenix, another in Houston TX, they go looking if I find something really interesting), they all needed extensive interior work, new dashes, full paint jobs and window moldings.
Everything else was like brand new, underneath the fasteners still have the torque markings visible and zero rust, the drivetrains and suspensions are great. Perfect straight rust free bodies make a great foundation.
Stuff in the rust belt totally depends on how you use it, drive anything decent in winter you are really taking a lot of life out of it. That's what beaters and old trucks that can have a plow hung on them are for unless you lease or trade in every few years and couldn't care less.
No matter how well you coat them, how many times you wash them underneath they will rot, some worse than others but it gets em all in the end. Almost every job involves smoke wrenches, splitters, taps and die, LH drill bits, cutoff wheels, BFH and chisels, and god knows what else. The one thing that does not get much use are extractors, the fasteners are usually so badly rotted the extractors break off causing an even bigger headache.
Suspensions are shot to pieces, bushings blown out, bent wheels, rocker damage, exhaust rot off, oil pans and diff covers rot through, they are just ruined. Broken frames from rot are also common.