"Business and Legal Forms for Illustrators" by Tad Crawford
"Graphic Artists Guild Handbook: Pricing and Ethical Guidelines"
"How to Write and Sell Children's Picture Books" by Jean E. Karl
"Writing and Illustrating Children's Books for Publication" by Berthe Amoss & Eric Suben

"How to Write, Illustrate, and Design Children's Books" by Frieda Gates (out of print; get at library)
"Writing with Pictures: How to Write and Illustrate Children's Books" by Uri Shulevitz