Nearly all under $30k are a first model year ('08), and include a 6 speed trans, not the dual clutch. It's not the way of the world nowadays, but your left leg won't mind the activity.
Ideal mileage for the price is in the 50,000-80,000 mile range. Given appropriate service documentation, we wouldn't hesitate to start E9X M3 ownership at this mileage.
For less than $30,000, the E9X BMW M3 may be the most obvious no-brainer buy out there.