Considering the age of the car, I would only fret about paperwork.
If it's a salvage title, stay away from it. Some vehicles can never be corrected depending on the nature of the accident and the repairs performed.
Abusive treatment or lackluster maintenance shows up pretty early in the life of a vehicle...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car