Actually for all the attention that the top Youtubers get (in terms of revenue), the reality is that it's going to be impossible to replace teaching income with popular Youtube videos alone.
Based on what I've seen, 1 million video views on Youtube gets you something like $5-10K. And that's with a primarily US audience that has the higher CPM / RPM. So your channel(s) would need to get to about 6 million views per year, primarily US driven, in order to get to earning a median US wage.
to get 6m views you need to make one video a week that gets 114k views 6000000/52 = 115,384.61.