The marketing and business courses will serve you well throughout your career. My advice for students who want to run their own firms is to finish school – concentrating on design – and then work as a designer for at least five years. In that time you might work for a variety of studios and in a variety of locations. You’ll learn a tremendous amount about how design firms actually do business, and make a good amount of contacts as well.
After you have a few years of experience under your belot you might be ready to start out on your own. At that time you’ll also have a better handle on the types of people you’ll need, equipment, office space, etc.
Of course, I did not follow that model, and now, with almost ten years experience running my own firm I’m a little more knowledgable about how is should be done…
Good luck!