When something is provided free of cost it won't be getting much importance as the premium paid courses. Rather than starting the service with few friends, try to find more people who are all interested to learn more about it. As it is entirely new when you start a new course it is difficult. All the above when you don't get back any revenue other than the learning while teaching might make you go for it without much of dedication.
Teach them the basic of everything, from how to create wallet, what are the different altcoins, what is the differences between them and so on. It could help them to widen their knowledge and at the same time they could avoid those projects that will make them fool and waste their time.