From my own personal experience of working online, I do feel that I could teach others how to make money they way I make money and give advice on what they would need to be successful at the kind of work I do online to make an income.
There may be other things that I could teach as well that I know about through other means and that I have done myself but I feel freelancing would be the best one for me to teach with me having a lot of experience in that field.
Honestly for the most basic aspects of how we make money online, they can be taught very easily but the problem is those being taught. Some of them think it's a get rich quick scheme where they will make a huge amount of money over a short period of time. When they see it's not, they will lose interest in learning.