Well how much do you think your work is worth?
If you charge $10 per panel and it might take you two hours to get it all done, are you OK with working for $5 an hour?
Be realistic in pricing your worth (at least minimum wage where you live) and don't go too low as a compromise.
Though just don't get your hopes up too much. If he is a big artist, he might not want to take a risk in working with someone with not a lot of experience. Yes, it is unfair but this is how most things go. You might need to work on a few smaller projects (your own or others) to prove that you have what it takes in regards to schedules and quality control on a time limit. Your art might be fine, but its those other aspects of drawing that are equally, if not more important.
Don't get me wrong, go for it. You won't know unless you put your name in, but most people will pick experience over inexperience.
Good luck! 