I know authors don't hire the illustrator but what if you found the perfect artist who's willing?

If you're self-publishing, that is fine. I only hired an artist after trying agents and then went the self-publishing route for my first book. If you're sending the book to agents, I would say avoid the extra money, trust the publishing house, and share your vision of the art when asked. They will generally hire their own artists because it fits their own format requirements, not yours. Hope that helps! I love having art done for my books, but it's a real time waster when you could be editing. I would suggest keeping his number to do promotional art later for your author website, posters, etc.