I need someone to find what the typical terms are for a business
manager of talent.  For example, an artist (the talent), typically has
a business manager who helps him/her set strategy, manage affairs,
evaluate deals, etc, and separately, an agent, who proactively books
the talent.

If at all possible, I'd like to see sample contracts between the
talent and the business manager.

I want to know what the typical terms are of such a contract -- how
much the business manager gets paid, what his/her responsibilities
are, how long the contract is, whether there's a fixed fee or a
performance fee (a commission) or both (or even something else), etc.

To be more precise, this actually has nothing to do with the music
industry; rather, it has to do with a very well-known author for whom
I am considering becoming the business manager.

Maybe this is what you mean:
http://www.writers.net/agents.html

This site has a draft contract, but you must be a member to access it:
http://www.nwu.org/book/agents.htm

And this site is directed at your "talent" warning about problems, so
maybe it is also of interest to you:
http://www.sfwa.org/beware/agents.html

Please don't consider this an "answer" to your question.  I am sure a
G-A Researcher can provide you with more and better information.
Myoarin