Dungeon & Dragons Campaign

I am currently working on writing/publishing a series of One-Shot adventures for 5th edition D&D and would like to include art in them. I am searching for an artist that can create multiple character/monster images as well as a few landscape and item images. In total, the series would consist of 21 booklets, each likely between 20-30 pages. I am currently in the planning stage and am trying to get an idea of the budget. Thanks in advance.