In this crazy business called writing, there's little certainty and a ton of variables. Money, particularly, is a dicey subject, and one most writers hate, all for various very good reasons. First, the author is normally on the bottom of the money pile. Unless you're Nora Roberts or Stephen King, of course. Most writers don't divulge their advances, which is the only real chance the writer has to make some moulah. A few are amazingly up front about money, and Susan Beth Pfeffer is one of them. There's also a "Show me the Money" list compiled by RWA's Brenda Hyatt, that lists the range for advances for most publishers. Check out her website - it was listed there once upon a time.
If you would like a detailed explanation of how advances and royalties work, check out Susan Pfeffer's blog entry for June 23, 2009. www.susanbethpfeffer.blogspot.com. I couldn't have done a better job.
I just read Pfeffer's Life as We Knew it, a YA about a world lost in climatic chaos after a meteor collides with Earth's moon. I loved the book, and it continues my reading streak of YA winners. I declare, YA writers are the best in the business.