I just made a clickbank script (PHP & MySQL).
Its actually a clickbank memberscript thing, and I really dont know how much to charge for the product, and so on.
When someone "signs up" for your product, they are getting to the "download page" and at that page a login is created for the user and username + password is emailed to the user, now they can log in and you can decide what they may see and not to see.
You can at the same time send an email to all the users which have signed up.
How much should I charge, and is there something you don't understand, ask.