Radioactive is right. Some of the Z3s have rear subframe issues.
BTW, the price is not too bad, but I think if you keep searching I think you can find one cheaper. I think the Z3 is a very fun car and with the 6-cyl, it will be a lot of fun to drive.
I really miss that BMW I-6 torque. The 6 cyl Z3 is a pretty quick car, but the M roadster is a beast.