>>90Pay is at the fair market value, based on artists that charge commissions on hentai-foundry.com
Depending on your skill level you could get $15 (US currency) per full-color character drawing for low skill, up to $50 per character for very highly skilled and in-demand artists (top talent). The average artist charges about 25 to 35 dollars per character, usually 50 dollars for a two-character sex scene. Backgrounds are an additional charge and so on. Everything is negotiable concerning the particulars.
I would envision paying for a character drawing, then a lesser charge of 3 to 5 dollars per an additional layer that contains a facial expression. A "Sprite" set for a character will consist of many images but we can re-use a lot of the art. For example, we might have one character with three poses, each pose has two possible outfits, each pose has ten different facial expressions. For one character that is 60 images, and that is just to support the standard visual novel scenes, not cut-scenes or romantic scenes. Consider that we might have 30 characters and that yields 1800 images, up to 2000 with the custom scenes. This gives us considerable expense, but consider that we don't need everything done in a single year, so the funding should be available even if it just me and not any other VN team members contributing. To do thirty characters without custom scenes I am thinking that is just under $12,000 and that the funding would be made available over two years without issue. That is $500 per month to do maybe 30 hours of work, depending on how fast/good you are ($16.66 per hour). These are all just guess values, the actual value is going to have to be negotiated based on what you are willing to work for and what I am willing to pay. Once you get going you may find that it takes you longer to do the work to meet a certain level of detail and your effective hourly rate could end up being less when finally calculated, who knows? Please understand that I am willing to pay what is fair market value comparable to professional artists, so hopefully you won't be offended or upset and enjoy making some regular income for drawing lewd and sometimes worse.
I have a few different VN projects that I'd like to contribute to and code myself, so if you as an artist are willing to do everything from loli to gore, you could make a fair amount over multiple projects. I realize that every artist has some moral breaking-point so if the work is difficult for you we can talk about it… I'd still like to get a decent or better artist some work and make these various Visual Novels concepts a reality.