What do you guys consider to much milege on a used gt3? ( im trying to stay under 10k, - i've heard instructor's say these cars are bullet proof, but im having a hard time looking at cars with over 15-20k miles, am i wrong with this?)

What is the breaking point to consider.. I'm looking at a few 07 gt3's..
Options on the car:
What options are a must have?
( the car is going to be primarily track car with some daily driving from time to time...)
thanks guys..