I have to disagree with Dennis a little on this one. I am from the South but I lived up North for about 10 years where I saw what happens to cars in 4-5 years. I even owned a 60 up there that was so rusted out that the body bounced off the frame rails whenever I would go over a speed bump.
I purchased an 02 100 Series last year that lived its whole life in Chicago and all it took was a full day underneath it with a wire wheel, steel brushes, Rustoleum and rubber undercoating and it was good to go. Yes, they do look horrible at first but there is something about the LC steel that is more resistant to corrosion. I was surprised (and elated) at how easy it was to get the rust off. After an hour I was certain that everything I was looking at was just surface rust.
Maybe the PO (a doctor) had a short commute and had the truck garaged at both destinations, I don't know. I do know that 10 years in Chicago will destroy lesser vehicles.
No worries on the disagreement. Mine was showroom clean underneath when I got it so no comparison for me to make. I was just trying to convey that my 'rust beware' warning wasn't meant to imply that they're rust-prone vehicles.