need help and advice 1990 iroc z vert
 

Hey guys I'm new to this and I'm in the process of buying a 1990 iroc z convertible off my cousin with 99k original miles and I'm wondering what a fair price to pay for it. I know they are pretty rare or "uncommon" since only about 1200 were produced in 1989 so I'm wondering what's a fair price and what are the most common issues with this car and mileage. I know it's a real iroc z because it has the yellow z28 badge on the dash and has the z28 rpo code in the*center*console. Any input will be greatly appreciated