Is purchasing a used cayenne over 70k good?

I don't see an issue with buying a used car with mileage. But when buying any used car, especially an expensive one, have a garage inspect it for you before purchase. Get it on the lift, check the electronics, brake, tire, suspension, etc. Money well spent. With a Porsche, use a Porsche dealer service department or a local independent garage that works on German imports. Good luck on your search.