Accounting and tax services take the top spot on the list of the most profitable type of small business with a generous 18.4 percent net profit margin followed by real-estate services (15.2 percent), law firms (14.5 percent) and doctor’s offices (13 percent) reports Sageworks, a financial data service that analyzed. If you are looking for a small business idea to kickstart your path to entrepreneurship, you are in the right place.