Design of fantasy book cover + internal images

Basically I need somebody to design a book cover + internal images for the book, black and white images for the internal images and one per chapter(5-6 chapters per volume) it is an ongoing project with the first volume to go on sale hopefully within 2 weeks. I can't offer up front payment but what I am willing to offer is 20% of all royalties with your artwork inside. Whether that ends up being $4 or $4000 I can not promise