I guess since we have owned so many I should point out the common problems with them.
Differential fluid on auto transmissions is RARELY checked since it isn't common to have 2 places to check the trans fluid. Just about every car we bought was low or basically out (mine had ~2oz in it). If this isn't fixed in time, the transmission will start to skip gears as they wear out and a lot of people will try to sell the car saying they think it is the axes going bad. Couple of the ones we looked at could go forward if driven easy, but couldn't back up.
Clucking or shaking on bumps/braking in the rear end - Between the struts being bad (over 200k miles on origs) and the bushings in the arms that hold the wheel bearings like to wear out. One of the cars we bought the person stopped driving due to "brake problems" which was just bad arms in the back. 350k miles and runs great yet
.
Oil leaks - That is how I got my car I drive now with 300k miles. Front main seal, cam seal, oil pump seal were all leaking. This caused the timing belt to go as well and they had it fixed and after that it had no power and sold the oil leaker with no power for $650 which had a new $600 exhaust pipe from manifold back (installed price). Well the guy that worked on the car didn't know how to install the timing belt..... 35 degrees OFF and it ran and drove well enough to make over 200 mile trip home with it (weak on up hills).
Bad engines - Bought a couple of these for transmissions and body parts. Basically every one we came across failed due to driving error. The engine leaked oil and the owner kepted driving it when it ran out. One that comes to mind had the oil pan off and told us stright up the lower end was shot from it. We moved it around the yard a few times WITH NO OIL and it still will start up. Replacement engine is going into it now from a totaled car (t-boned).
Rust - Ok I better add this in, they do have a couple of spots where they commonly rust... only a couple spot though. Number one is anywhere that there has been body damage, which is kind of a given. Second is inside the rear wells at the back side. It does become a hole pretty quick (mine is about 3-4 inches around). That is about it for real rust, around the fenders is the next place they will start to rust, but it isn't very common unless they are in really bad conditions like the UP in Michigan where they dump tons and tons of more salt then my area of Michigan.
That is about every problem we came across. They seem to hold up really well in wrecks too. the T-boned car was hit while pulling out in front of a F350 truck going 55mph and we was able to barely dolly it home with the rear wheel rubbing and sitting about 40 degrees off
. When we got it home, it drove around the yard fine except the air leaks and the rear tire hitting the body. Even in the mangled doors, both window motors worked, rear one shaked like crazy from being bent so bad.