Take all of you operating expenses (advertising, phone, car, internet, computer purchases, etc, etc, if it can apply to business at all, it's a right off, even dinner and drinks in certain situations), then subtract your operating expenses from your total revenue (that = your profit = all you pay taxes on).
Also, you'll get tax breaks if you file an LLC or Sub S and employ yourself through your company (in the future). If you are a sole proprietor then you'll probably get hit with self income tax. That sucks, extra 15% in Missouri, wont make that mistake again.