I looked at a v8, with 52K, the car drove nice, but the underneath had a ton of rust. The spare tire was completely rusted. I expect a little, but not that much. ..
To me that would be indicative of a boat being towed and launched in salt water. My friends truck was like that. Then again he never washed it down. He washed the boat & trailer but not the truck, why? because it was just the truck he used to to pull the boat & he put little importance on it, hence oil changes were not done on a 3 month schedule but evey 3k miles which could take a year. Whiich would mean the filters were rarely changed (hey the truck started and got him to the beach ramp)... So am I showing you the pattern?
My 2002 Sport Trac had 74,000 miles when I bought it from a Ford Dealer. It was a trade in. It was clean. All recalls addressed, all documentation present, all service records available.
For me, when buying used I use several steps for piece of mind.
1. I prefer new car dealers
2. I inspect the car (fluids, tires, hoses, belts, air filter) Usually a dealer will change these. What I do check is undercarrage, interior (not the obvious look at the edges, on the bottoms etc to see if the car has been scrubbed down.
3. I make sure the dealer will guarantee state inspection (not done by them)
4. I insist on a 100% warranty by the dealer for at minimum 1000 miles/ 1 month with an option for the extended warranty within 30 days.
5. Carfax report
6. Warm & Fuzzy (most important) If ANYTHING gives you a bad feeling (car or dealer), Walk Away. Don't compromise or accept reasons. There are more trucks out there.
Of course nothing will guarantee that the vehicle wasn't abused but it will minimize your risk.