Public speaking goes beyond you wanting to make money but rather what you are marketing to the people. Take for example motivational speaker, Valeria Levitin who decided to do what she was doing because she wanted to help people fight against the disease that is eating her which almost every woman has, wanting to be small or thin and how far they can go to reach that goal. Find out what you want to market, and make sure you are talking about something that you are well versed with and passionate about. Good luck.