Last month author Laura Purdie Salas did a blog post called [my writing life] How Much Money Does a Writer Make? (2012 edition) in which she described her income breakdown. In the writer circles I've bumped around in, she's not doing badly. In fact, I know plenty of people who would think she did pretty well last year. What's interesting is how many different types of writing-related work she had to do in order to generate that income. Money from trade book sales, which is the way most people think writers make a living, was quite a small portion of her overall income. She has links to her income from several years back, and even in years when she's done better over all, it wasn't because of a lot of money coming in from trade. Even if you add what she made from work-for-hire books to the what she made for trade, so that we're counting all of what approaches "traditional" writer income, we're not even getting to half of her take for 2012.
She has done what seems to me to be a good job of going out and finding writing-related work. The time involved in managing all those different work tasks makes me want to curl up in a little ball.
Writers interested in the work-for-hire writing can find information on the subject at Rachelle Burke's Resources for Children's Writers (Scroll down to Item 14) and Evelyn B. Christensen's Educational Markets for Children's Writers. Both those sites were brought to my attention by Kathryn Lay in her article Writing for the Educational Market in the March/April 2011 SCBWI Bulletin.