John Scalzi’s put up a couple of recent posts about the business of writing. The man knows what he’s talking about: he made over $160K from his wordsmithing skills last year.
If you haven’t read his books, you should; they’re straight-up science fiction with good characters facing tough choices, and he has a very easy to read prose style. Start with Old Man’s War and work your way forward from there.
In the meantime, head over to his blog and listen to his advice on making it (financially) as a writer. They’re long posts, but they’re well worth your time.