shimazu makes a good point about replacement parts and receipts. Even with only 75,000 miles, the age of the car itself means a lot of parts will need to be replaced (or, ideally, have already been replaced). If the owner knows what they're doing, they should have, at the very least, documents showing when major repairs/replacements were done. If they're unable to provide you with receipts of work done on the car, that's a red flag. Get them to pay for a CarFax (or similar) report on the history of the vehicle (that will give you the number of owners, where the car has been registered in the past, etc).
A few years ago my brother nearly bought a car that was a really good deal but then we got the CarFax report and discovered that it had been registered in New Orleans, LA during Hurricane Katrina. Red flag right there. Its things like that that you'll never know unless you get access to the history behind the car. Plus a decent mechanic (or at least a friend who knows their way around cars) will be able to tell you the condition of the body (as mentioned, if the car has been driven/stored in an area near an ocean and/or in places where salt is on the roads all winter you should probably pass on it).