I$20/hr is the usual starting salary, I've heard some places give more, some places give less. You will have to try out, take a qualifying exam, and then go through the training process, so get in touch with folks with your office and find out when the next trainings are. You get paid $8.10/hr for training, with no guarantee of being certified to teach. If you pass training, you will get your first class.
Teaching, tutoring, and online work are all done on a "who asks for it first" basis, so I find the working hours pretty flexible. Some markets ask for more help from younger instructors in terms of marketing on campuses, getting membership rosters, etc... But so far I've found the job to be pretty simple in terms of flexibility.
It is a huge commitment though. Especially if you are a pre-med yourself, you'll be teaching fellow pre-meds, and you have to know your stuff if you're going to survive and get a chance for more classes. This is why trainings are usually graded harder on pre-meds, because it's harder for you to command respect from a class without being a total *******. You teach 2.5 hour lectures, and need to spend time preparing for each (they will pay you the $8.10 rate for up to 2 hours of prep time per class taught).
It's very loosely organized, and if you're looking to make bank, you're not going to do it very quickly. If you're looking for a few extra bucks, it's an awesome job to have if you're good at teaching 😀