For only a couple thousand dollars I would expect to find multiple issues with a used toyota from the 80's and 90's. And even more so on a purpose built offroad rig. Knowing what to look for is good but there will always be unforeseen problems, hopefully minor but possibly major. Aside from visually looking for leaks, listening for odd sounds and going by feel during a test drive its hard to find everything wrong with a used vehicle. It could take hours to go through everything and I bet there would still be issues that get overlooked. When I was young my parents always recommended getting a diognostic check done by a mechanic before buying, but things can still be overlooked or parts that were fine can fail the next day. I can't think of anything specific to buying a used Toyota that you wouldn't look for when buying any used vehicle.
I spent more than a couple thousand on a rig that I hoped was close to turn key and later found frame issues that have kept me from using it and is going cost $$$ to repair (I don't have the skills myself). I have found a bunch of issues with this truck, mostly minor or what I would expect from a used wheeler, they add up but the cost is minimal and I can do the work. I guess what I would recomend when looking at a used wheeler would be to look closely at the frame and any fab work/welding that has been done.
