I would like to sell book and course materials within each course. I've search plugins to no avail and nothing.
It needs to be an option that a teacher can use right inside the course.
On a separate note, I would also like to make it possible that teachers get paid directly for their courses and moodle only take a percentage of that instead of moodle receiving all the income and then paying the teachers.
The beauty of Moodle is that you can make your own plugins, or get someone to do it for you. You can offer such a plugin in the Downloads section, or ask for a fee for contribution to development and maintenance costs. Your choices.
The payment of Teachers though, that is a process that I would have thought may be automated at the payment portal. Have a serious look at the options available; but I would suggest this is way outside Moodle's ambit and nothing to do with Moodle.