I am a freelance Illustrator with most experience in children’s book Illustrations
Throughout the process I sent low resolution copies of the pages I’d completed to show the author that progress is being made and to allow them to suggest edits before I get too far along. For example, if they decide the main character should be in purple instead of red I can change 5 pages then move forward with less editing after the fact.
Me: Here are the first pages, if you this is good I’ll do the rest.
Client: looks great!
Me: Here are the last pages. If you like I’ll send full resolution of everything after final payment.
Client: I love it! Here is final payment
Me: Thanks! Here is everything in final format at high resolution.
Client: I need you to edit the outfits on every page.
Me: …I can’t do that with out charging you more. That’s why I sent you pages to confirm.
Client: I’ll take them to someone else to have them edited!
Why would he pay someone else to do exactly what I could? The answer: to convince me to do it for free.