I would like to enroll my company in to the iPhone Developer Program for $99. I have a few questions, which I can't really find an answer to, because Apple aren't very detailed in their pages unless you actually registered.

So here goes:
1.) Is the $99 paid yearly?
2.) It says when distributing free apps there's no fee, but if I want to distribute a $0.99 app, what is the fee then? Is it huge? Or..?
3.) Can I keep track of how many people bought my app anytime?
4.) Is there a page on the internet where I can read more about app store distribution that explains almost all the info I need to know? (Apple doesn't satisfy me on this)

Thanks