I bought my Z3 used with 86,000 miles showing. It has many of the typical flaws of this car. Sagging glove box, sliding seats, leaky top, seriously crappy sound system, and cracks forming in the rear subframe. It will be worth the price of admission once all the gremlins are finally taken care of.
Just a quick comment: the sagging glove box is very easily fixed either with some custom kits sold on the internet for around $70, or, like me, just grab a couple of 1.5" drywall screws and screw them into the flat "meeting surface" on both sides of the lock panel, they will re-align the glove box to where it originally was and no more sagging problems.