Things to pay attention too on the 1980-1996 F-Series trucks...
1. E40D tranny's. They are notorious for going out anywhere from 100-175k miles. I know thats a broad spectrum, but its really hard to tell. Some will make it longer if they were very well maintained and had an external tranny cooler. Mines at 149k right now, and seems to still be shifting strong. I'm dreading the day it goes out, because it will be an expensive repair/rebuild.
2. The 4.9, 5.0, and 5.8's are all pretty strong engines, and seem to go for awhile. There are guys on the Bronco forum that have over 200k on them. But they do get tired nearing 200k miles, and most typically rebuild at that point.
3. Rust...around the wheel wells and tailgate.
Other then that, they are pretty solid trucks.
I dont know much about the 97's-02's. My buddy has a 98 F250 with the 5.4 and its still going pretty strong. I think he's at about 170k.
Honestly, for only 3-4k you are going to have to get one thats in need of some repairs.
TOTALED DEC. 2014...05 XLT 4x4
Replaced with Blue Jean Metallic 2014 SuperCrew F150, 5.0 Coyote, 10% tint, Hell Bent Steel Leveling Kit, Allied Duals, Weathertecs, Uniden CB