[Dutchie987]

Think about who your competitors are.

YouTube has (non-live, granted) courses on everything. And then there are the specialized course-ware sites. Many of them have a subscription model of "all you can eat" for a fixed price.

Your unique feature is that your courses are live. That is great for interaction with your audience, but can be a risk if you have a one or a few people that like to hear themselves talk, you know what I mean.

Live has also a drawback of necessarily being a scheduled event. How many potential clients do you leave out because their schedule doesn't fit with your lecture times?

All in all, I think it's a good idea, and can be very lucrative, if you find the right subjects and audience. Find that niche and you're golden.