Well, that job sound great for you and you seem very interested in it so just forget about the money and get it. Dont try to negociate too hard, just ask about the salary progression because after all, this is the most important thing!

If you need a base number for salary do as I said: call some university/art school and ask how much their graduate get. They will be willing to supply this number and you can start from that point.

Good luck!