Look for a history of regular oil changes at a reasonable interval, hopefully with a name brand full synthetic oil. This car puts out a fair amount of power from a small engine which is pretty highly stressed, and it particularly needs good quality clean oil in it.
Also, if someone took the time to do that, it's a good sign that they cared about the car in general.
The cars have generally been quite reliable.The engines are used in the formula Ford racing series with only a dry sump oiling system added. If they can stand up to racing, this is a good sign for their durability on the street.
Good luck in your search, the cars are a lot of fun, I hope you find a good one.