Several years ago, I pointed out John Harrington's great book, Best Business Practices for Photographers. Since that time he's put out a second edition that has even more great information on photographic business practices so I think it's worth pointing out again.
I highly recommend John Harrington’s book even though it’s aimed more towards the editorial, advertising, commercial photographer, there's tons of great stuff for real estate shooters as well. Especially informative are the book’s many “case studies” covering a wide variety of topics where Harrington includes actual contracts and e-mail conversations with clients. His pricing policies and thoughts on getting paid what you deserve are enlightening.
I believe Harrington's book is a must have for real estate photographers.