I'm looking to commission some character art designs intended to serve as a basis for 3D character modelling. I suppose this will mean front and profile views of the characters in "T-pose", plus some additional face drawings for emotions (i.e. a "model sheet").

I expect to pay some kind of advance on this, and then offer the artist some percentage of revenue through "Creator Endorsed" sales of the end product (which will be an animated video series released By-SA on the internet).  My biggest question is how much of an advance should I expect to offer for this kind of commission?

Secondly, since there are a number of experienced 3D modellers here, what do you need exactly in terms of design art to create a character mesh for high-poly animation work?

BTW, I will probably be back with lots more questions... we are just starting work on this project, which is called "Lunatics" ( http://lunatics.tv -- though I'm afraid it's only a stub at the moment ). Of course, it is a video series, not a game, but there will be plenty of cross-over, and I'm sure you can see that the needs are similar.