Good day,
I have been developing elearning websites for over 15 years. I will be shorting here.
To create an elearning website for you to provide services for others to create their own courses and their own audiences and maybe sell their courses, this would be a systems to host as many as you like of the vendors, you should be expecting this to cost somewhere between $5000 & $10000 depending on your feature requests.
If this is likely to you, please communicate with me.