Aaron Doucette is the guy who made and maintains my appraisal website and he uses referral fees to keep his sales pipeline full. He explains how this could be used to create a part-time or supplemental revenue stream for you.
Learn more and see his portfolio at http://www.aarondoucette.com/
The Invest Local Book blog is all about small business, local investing, home economics, small business systems and borrowing money for your business. It's full of great content and I look forward to seeing your feedback.