Get any used car checked out. It's completely luck of the draw as to how the vehicle was kept up, etc.
For example, when I got my Trans Am (summer of 1999) for $4k, I quickly found out that the motor was trashed. I had to replace the engine less than a year after getting it. It runs great now, but...lesson learned.
On the other end of the stick, the TA was obviously not the car to drive in Michigan winters. So, I went to a local Chevy dealership with $200 (yes, two hundred dollars) in hand. I needed a car to last me for 3 months, at which point I was planning on getting rid of it. This was November, 2001. The salesman took me over to a row of beaters, sitting off to the side (the trade-in lot). I drove out of there in a 1992 4 cylinder Mustang for $200 out the door, taxes, title, plate, registration all included.
I later learned that this car had only 42k original miles on it - not 142k as I had thought (Carfax). After a couple relatively minor repairs (new radiator, seat track, door handle, and door needed to be re-hung - all done myself for the cost of parts, except for the door hanging) it was very serviceable. A/C was ice cold (and still is), everything works great. I ended up keeping it, and it's now at 62k miles and runs excellent. In fact, I just took it on a 1,000 mile road trip, and it never skipped a beat. Not bad for a car that cost me about $500 altogether.
Moral of this story, something could be priced way cheap and be a diamond in the rough, or priced fairly high and be a lemon. $$ is not always an indicator of what you're getting. Have a mechanic check out any car you're considering top to bottom, and run a Carfax report on it. My .02. Good luck!