Most children's writers publish about one book a year. Publishing houses pay around $10 per page of manuscript, and around $15,000 for the rights to a completed book. Most books have initial print runs of 15,000 copies, and authors take 10 percent of the sales.
Authors of famous and successful books can earn a great deal more. Books turned into films especially make very large profits, often running into the millions of dollars: JK Rowling, creator of the "Harry Potter" books, makes over $30 million a year.
Most writers cannot support themselves only from writing, and have a full-time jobs to provide regular income. Writers may leave these jobs as they become more successful, and able to support themselves with their writing. Children's writer Louis Sachar worked at a warehouse and studied while writing his first few books--one of which was made into a movie.