http://www.carfax.com/car_buying/used_car_buying_checklist.cfm - When you are buying used cars, what you need to mainly know is that the car you want to buy is a valid vehicle. The problem with buying used cars is that it can be difficult to verify that they are legitimate. When it comes to reports, car salesmen should be happy to provide you with a range of documents that can help confirm the identity of the car itself.