How dare you sell a course?
Once in a while I see some people complain about so and so selling a course on some subject. Their main complaint is that this person is not making that much money, or is not really an expert on the subject. I find this type of person very toxic. Ignore them for your own good.
There's nothing wrong with selling courses on subjects you understand, no matter your level of expertise. There will always be someone who knows less and to them your course may be good value.
The only issue I have is if the course makes false promises, or masks the full truth. As long as you are honest about it, I really don't see a problem.