It really depends on the truck, the mods/improvements done to it, the paperwork trail etc.
For instance:
I bought my 1990 M923A2 for a VERY reasonable sum. (Not stating because it really was a brother-in-law deal). It was titled for Offroad Use Only.
This is what I recovered:
Since that time, I've gotten the title straight so I can use it on road (which was a months long process), registered as a Former Military Vehicle (huge process in and of itself), rebuilt the PCB, installed many extras (backup camera etc), re-covered the seats, painted, replaced the bows and canvas, bought add ons for the trailer etc so now this is the truck:
And this is the trailer:
I've also done some "minor" stuff, replaced canvas straps etc.
All of this has to be taken into account when you're looking at a truck to buy.
Not to patronize you or speak down to you, but these aren't assembly line trucks like the Fords, Dodges etc.
2 trucks can have VINs 1 digit off and be completely different as far as mileage, mechanical soundness etc.
What you need to think about is your budget and what you want to spend up front vs down the road.
If you want a road ready no issue truck you can register and insure and drive down the road, be prepared to spend $15,000+ (and that's really the low side).
For a "project" truck or one you'll have to do a paperwork circus with, you may spend less.
At the end of the day it boils down to how much you're willing to spend, what you're looking for and how much work are you willing to do before you can enjoy the big beast now sitting in your driveway.
There are plenty of members here with trucks for sale in just about every stage you could want, from frame up resto jobs to "turn key" trucks you can enter into a show.
Best of luck and if I can help at all, feel free to ask here in the thread or in a private message/conversation.