Car Fax
Car fax is good to show how many past owners and any major damage. It will not show minor accidents, core support damage, clamp marks on the frame, turned bolts, major paint work, or flood damage.
Also be wary if a car has been re titled in another state.
These are things you should ask the dealer in writing such as , does this car have any hidden damage that I should be aware of. Such as core support damage, turned bolts, clamp marks on frame, major paint work or flood damage. If they do not answer you run for the door.
Bimmer