Get a third party inspection done from a authorised service centre, it would cost around 2 to 3 thousand. OR else take a dentre and a mechanic to check the car for major accidents and mechanicaly the condition of the car.
Other guideline wont help if you dont know how to check.
-Repaints, sprays on rubbers etc. Peice to peice paint shade, the mirror shine bla bla
-Suspension sounds, engine oil, radiator, smugde under the oil cap, bla bla rust in/under the car