Not charging for training is a great way to make sure you're not whoring the art. When I teach, which is rare, I teach for a beer when we hang out afterwards. On the other hand, we want very experienced and knowledgeable people to continue to teach, so they do have a right to charge for classes. At one time, the experienced people had a monopoly on knowledge. That's not so much the case anymore. That's the problem with teaching. What if they don't care? What if you know they don't care and you also know that no matter what you say they'll keep doing exactly what they're doing? What if you know that if you say something, they'll embrace that asp even tighter out of perversity? I've had this discussion on and off with students, usually intelligent and in their early 20s, where they want to tell me that aikido is the most awesome art or tai chi is the most awesome art because you can vanquish numerous assailants without harming them or breaking a sweat. I used to try to tell them the error of their ways. Now I just say "Whatever." The reason isn't because they're right, it's because by arguing with them, it makes them think that we're just two guys arguing and therefore equal in knowledge, which is not correct.