Illustration for a childrens’ book

I am currently writing a book for young children and I would like someone to do the illustrations. given that it is a book for young children, the drawnings and illustrations play an important part as the book needs to be very visual.

I still haven’t finished the book but I am currently reaching out to get an idea of budget. I am expecting it to be 22-30 pages long. All characters are animals. I would like something very lively and colourful. By way of example, I realy like the illustrations by Axel Sheffler in The Gruffalo (https://www.gruffalo.com/).
Could you let me know how much you would charge for this project? Many thanks,