Good question Brian. I am always a fan of a free trials or even better, the free tier. The later you have to watch out as you could be stuck a situation where you can't convert people to the higher tiers, but all in all what you are trying to do is show people the value your product provides and the best way is to have them see it with their own eyes. Once the user sees the value your product brings them then they will easily jump on board to becoming a paid customer. Also, be sure to get feedback from your users, especially ones who convert to paid customers. You could interview them or survey them understanding what value they got out of the product, but the paid customer provides the best insight, none paid can sometimes have you chasing your tail! Good luck and keep hustling!

I would assume it depends on how crowded the topic your teaching is. If there are hundreds around the topic you would want to have a unique spin on it, even then it maybe hard to stand out, increasing your CPA (cost per acquisition) . Also udemdy takes a 90% or so cut from the leads they bring to your course.

You always want to mitigate risk, for you and for investors, or partners. One of the easiest ways is creating fake landing pages of your product idea. You then run ads, fb or Google, and see if people 'convert'. Convert can be giving their email, clicking a button like buy now, faking all the way to checkout, whatever you think proves there is a market and need for a solution of your product.

There are many other ways to test a product without building. I would suggest you pick up the book Lean Startup by Eric Ries, as he is the founder and master of the MVP, minimum viable product. If you have any questions, feel free to reach out as I was in a similar situation with my venture and in the EdTech space.