What kind of car is it??
Most mechanics will charge anywhere between $100-300 (depending on if it's an import/domestic and of course if it's a MB/BMW/Jaguar/Audi expect to pay higher) to do an inspection on the engine of the vehicle checking the: oil, fluids, battery, belts, leaks, ac/heat, tires). If you can do this yourself, you can save some $$ as it's not hard to perform those services yourself.
Most mechanics will not check the body of the car for any bondo fixes/repainting as it's not their specialities.
When I buy used vehicles I mainly do the checks myself and I follow these simple rules which may or may not apply to you:
First run a carfax on the vehicle... IMO there's no point in seeing the car when it already has a branded title or has a few known history of accidents or theft as it may be dangerous to drive and I already know the resale value is :-X.
Second if the carfax checks out I go see the vehicle. Do a quick walk around car jotting down any dings/scratches/imperfections you see. Pop open the doors/hood/trunk and check to see if all the VIN #'s are there untouched and matches. Depending on vehicle makes and models, the VIN#'s should be located on the fenders or near the engine bay, door jams, trunk, and sometimes on the bumpers. Also run your hands through the edges of the fender/door jams and feel the paint... the paint should be smooth and not have any hardened drippings or rough spots. Check the inner wheel well for any paint overspray or missing rivets/screws.
Third, if all that checks out you now move on to the engine. Turn on the engine when it's cold, listen for any ticking/knocking with the hood open. Look for any leaks around the engine bay, leaks underneath the vehicle, check the oil and other fluids... errr forget it.... just take it to a mechanic. It'll probably save you a headache