FYI: Even if you are selling a course at first, more than the upfront cost of the course, I think a bigger challenge is to get people to actually watch the content (assuming those will be videos/podcast)
I am sure everyone comes across tens if not hundreds of such posts on a daily basis, and a very few of them actually spend time to even watch those (considering those are free).
So your barrier to entry is not the money, but getting people to start watching it. Adding cost as another barrier in front of it will just kill the whole thing :)
PS: You cannot profit off building your personal brand. You profit off your personal brand once its built.