How much should I charge for tutoring?

I'm in college for Business and doing really well. My father is a business consultant and has taught me all kinds of business practices and principles over the years. Most of people in my cl ask me for free help, but it's gotten to the point that it's talking up a lot of my free time. I'd like to reduce the free advise I give and offer tutoring, but I don't know how much to charge? I don't want to be overpriced because I am just a student and not a professional.