I just found this cool site by a kid. Not all of the links work – she mostly sells stuff by linking to Amazon.com, and she doesn’t run the biz alone, but its worth checking out:
http://www.kidsroar.biz/kids_roar_home.html
If you are between 8-12, you can try to be a part of the biz team by getting sponsorships to be on the board of advisors for the company. Seriously cool opportunity if you want to see what running a biz is like without all the responsibility – just chillax and see your ideas work – BK Host Devon