I saw this KB article that may answer some questions:
Also this FAQ
- If charging for book, looks like you need to get a book ISBN number assigned and have a Tax ID for too as per FAQ
According to the Apple iTunes Partner Programs FAQ there are no start up costs. I suspect that working your way through the "Publish your book to the iBookstore" in the help system will answer your other questions.
Best of luck.
I've already read thru this info before asking. It seems you HAVE to sign up and give them a cc # before they will tell you what their cut is. WHY? This just makes me uneasy, and I would appreciate anyone out there that is using this service actively to pleaase let me know what the deal is. Thanks.