Ball joints
tie rods, rubbers can be cracked and durt and stuff can get in.
Wheelbearings
brakes
cop's is hard to check, if it's running good it's ok but the next day you can have trouble with one of them.
Check where the car had service and what is done to the car, all fluids etc. and sparkplugs and cop's, you don't wanna have a plug spit out.
check all electronics.
I always check under the car, flashlight and down under the car. oil leaks, rust and hidden damage you can check here.
Good luck and if you buy it, have fun!!!