I've not hunted for a cobra since I built mine, but I have purchased airplanes from afar before. Same issues. I would ask for a local forum member to examine the car for you. As others have suggested, think of all the questions you want answered and get a list together. Someone who is already an owner would probably do a more thorough pre-purchase exam than you since they will know what to look for in terms of build quality, performance, fit and finish, etc.
Good luck on your search. If you want to take a look at my Lone Star, let me know. My web site is
here