Some days I ago I found out a blog of an illustrator. Her name's Holli Conger and she is specialized in children's art.
Last month, she posted for a whole month a tip a day about illustration business. She wrote about clients, licensing, marketing, expenses and a bunch of other super useful stuff.
Down here there's the link to the first tip called "How to find clients". And I believe if you are starting out as an illustrator you definitely wanna read this... Enjoy, and don't forget to read also the other 30 tips!