Just my two cents worth.

Always go for the money. It costs them far less if they give you content. And never, ever, do a rev share arrangement with a model. First of all, you have no guarantee that the site will be successful and most importantly, they'll treat you like they own you after that. Business deals should always be transacted in a financial manner.

I'd be happy to help you understand how to value your work and what to charge on these particular projects if you want to PM me or ICQ me at 1 6 7 9 0 9 7 6 0.