the guy who owns it is gonna bring it by tomorrow so I can take a closer look at it...
what are key things to look for? (other than the obvious)
...check out 4x4.... put engine under a load and listen...
check out floor boards.... pull mats....
I'm counting on you guys to help me make the best decision...
what are things to watch out for? be wary of?
What I looked for when buying mine was:
First and foremost, RUST! Look EVERYWHERE! Especially on the underside on the frame. Also check where the sportbar goes to the body...
While you are down there, look for signs of heavy offroading (scratching on the skidplates and axles will tell the story here).
Then check the engine. This is not unlike you would do for any other rig/car/bike/etc; check all the belts, check how the fluids look and ask the last time they were changed (should give you an indication of how the previous owner took care of the engine maintenance), look at the electrical system (some owners do a real crappy job when installing after market stuff, me included!), condition of vacuum lines, and all that... But most importantly, listen for strange noises.
Make sure the 4WD (hi and low) are working; if the front is not engaging, it is most likely a vacuum problem, but do not assume that it is...
The condition of the top should also be checked; if possible, hose it down and see if there are any leaks. Not that this would be cause for not purchasing the Jeep, but you can negotiate the price down if it means that you need to buy a new top (this applies for both hard and soft tops!).
Similar to the top, the condition of the tires; if the tires are worn, you will need to replace them, and this is costly, so take it into account.
Also, driving the jeep can tell you if there are any problems (drivetrain vibrations, noises, loose parts, etc).
From my part, that's about it; I am sure others with more experience will give you more stuff to look at!
Felipe