Good question! The short answer is "It depends".
The long answer is I create a quote based on each brief sent to me. What factors do I take into my pricing? Things such as level of detail, backgrounds, number of characters, deadline and copyright or licensing agreements all play into what I price for you. Once I have all the details I need to write an estimate for you I'll send you an itemized estimate.
It's easy! Just send me an email with your brief, don't worry I don't bite!
Be sure to include in your brief a detailed breakdown of what you're after so I can give you a more accurate quote. Also let me know if you're on a tight deadline or budget.
If you're happy with the quote we can move forward from there.
Check out this article for more info: https://www.blurb.com/blog/how-to-hire-an-illustrator/
Absolutely not. In fact it can make the project prohibitively expensive if you want to own the copyright to the illustrations you commission. I do however recommend getting the copyright for any mascots you commission from an illustrator as they are akin to a logo and are part of a brand.
You will still need to come to a licensing agreement with the illustrator before you can use their copyrighted material.
Illustrators Australia has some good information on the subject here: http://www.illustratorsaustralia.com/tips/commissioning-guidelines/