Have it checked out by a good mechanic before purchasing. The car is getting up in miles to the point where some semi-major parts are coming to the end of their life span. Having said that, a well maintained BMW will outlast most cars on the road today.
My mom had a Z3. Nice riding car. The newer Z4 she has is much stiffer and harder ride. The one you have your eye on there is gorgeous in my opinion. Price wise, check out http://www.edmunds.com