I get asked a lot about payment/cost issues when it comes to illustration. While I'd rather be thinking about color and form, this is how I pay my rent. While there really are no set answers, (especially when it comes to cost), there are some great bits of information floating around the web. Here's one, about having a lawyer and solid contracts with clients. About 40 minutes, but nothing's visual, you can just listen if you're working, though there is NSFW language, obviously.
2011/03 Mike Monteiro | F*ck You. Pay Me. from San Francisco Creative Mornings on Vimeo.