Oh, bah. You're only what-17 or 18? You've got plenty of time to become a professional. I mean, you're a great deal better than many far ahead of you in age.
I had the very same aspiration when I was a freshman. It is possible, from what I hear anyroad, but not likely. Most authors you hear of are well into their thrities or at least mid-twenties before they have any popular novels out.