On the other hand, you could be the next Stephen King, or J.K. Rowling! You never know. But just expect that it's not going to make you rich.
That said, writing sure is rewarding and fun. It's pretty addictive once you get started, so maybe that's why 80% of the people surveyed in America said they were working on writing a novel. So go ahead, start on that novel you've always dreamed of...it may not pay off in terms of money, but you'll find a lot of personal satisfaction in the work. I sure do!