I don't think anybody mentioned that a KLR is kind of tall. If you're short leg'd, a KLR may be a challenge off road.
I was debating between a DR650, and a KLR650 for some time. Decided on the KLR because of it's luggage rack, better seat, and ( to me ) more highway ready.
I haven't been disappointed. I like that it can go 70 - 80 and still get me down that abandoned road.
Another thing to consider, if a bike has low miles, and old years, it probably sat around a lot. ( Carburetor clogging issues. ) I once tried a 21 year old NX250 with 7,000 miles on it. Rode it around the block, and seemed to run ok. When I got it home, and ran it a while, I discovered idling issues, and high speed running issues. Carburetor. needed to be cleaned. Check inside the gas tank for dirt, rust , etc.
Look for rust on the bike. If it's been outside, it may have rusted hardware, fittings, and like.
I may be wrong, but my thought is, If it looks clean, maybe the guy who owned it took care of the mechanics as well. Not a hard fast rule, but has some merit.
Try to get to know the owner. Put your "bull-shit" detector on while listening to him.
That's what basically worries me. I don't have vast mechanical background, so when I go to check out a motorcycle, I can look for out of place things (rust, leaks, obvious missing parts,) listen for out of the ordinary sounds, and feel if it's running rough. When it comes to alternator and battery output, I have an altimeter, besides the battery, don't know where else to put it.
I was in a similar situation. I went to check out a 94 Goldwing. Guy said he was in a tough financial situation and injured his back. Was having a garage sale with what look like everything he owned and he had a back brace. Took the Goldwing out. Rode perfectly. 120k miles but ran like new. Bought it for $2,500. On the ride back home i hear rushing air. When I got home, I noticed when I started it it had heavy blue smoke. Sold it for $2,100 because I maxed out my budget buying it and had to move shortly.
If there are minor things, I don't think I'd worry too much. I'm concerned about getting it home and it needing to be pushed to a mechanic.
Concerning the tallness factor, I'm 6'3"ish, I mounted an 07 KLR the other day at the dealer. The height was actually comfortable and I enjoyed the ride. Beside the wind. Wouldn't be too bad with gloves and a helmet or a larger windshield though.