this sounds silly but start at the "reputable" dealers in your area (usualy a new car lot that also sells used)
this will at least give you an idea of what you can get in your price range from a "safe" source. Also check auto repair forums (lots of free ones out there) for that make and model car. It will give you a good idea what to watch out for in problems. ( a starter for 1 car is $30 for another $400). I bought a beautiful buick from craigs list with what seems minor but became major issues with car. (not starting being a major issue) I replaced it with a 1995 Cadilac Concours Deville (no i didn't leave out an e) 1 owner car from the dealer. 183k when i bought 205k now and is probably the nicest car i ever owned (paid $675 for the car itself and about $1000 for total tuneup (brakes, cables, plugs, oil change, radiator flush etc) dealer already had another on the lot (same year a little lower milage (not quite as nice) for $3000. (i should mention i had a trusted mechanic friend working at this carlot)
Just don't walk in blind and DON'T ever buy the 1st time you go to a car lot unless u know and trust the guy (last but not least NEVER trust the salesman their job is to sell you the worst car for the most cash)
Another good idea is if you have and trust your mechanic ask him if he knows of a good buy (he should know after all)
Oh and most importantly Buy a Ford or a Cadilac and your all set hehehehehehehe
Ok a JEEP is not a bad 2nd/3rd choice (i still miss my jeep but not as much as my 86 full ton Ford Bronco)