Right now I'm in college studying Computer Science, and in my free time I write (I'm not any good at either yet, but now's the time to get good, so I'm not worried).
I've thought about a start-up, but the risk and reward are both too high. A successful startup is around the $10 million to $1 billion, depending on what you create. This is way over my goal. I'm sure the risk is proportional to the potential money earned, so it'd be inefficient to overshoot my target.