I actually had this conversation with a friend just a few days ago, about paranormal, classes, learning, and charging.
Here's my opinion on it. I was actually considering putting together some classes for several subjects. And when the subject of charging came up, what I said is that what I would personally do is provide the knowledge for free in one form or another. For instance on the forums, or in a feature or someplace where people can gain the information. But there will always be individuals who prefer to have hands-on training, in-person experience, and a classroom or field environment course. For those, I think there is no issue in putting a charge to it. At least in my mind there is not, since you're also providing the same material for free.