Reading the recent posts, I realize that I overlooked the obvious fact that chord families and keys are part of theory. Of course the new player needs to understand them; I always teach those things to a beginnig student. Things I leave for later include scales, chord construction, chord substitution, harmony, sight reading, etc. Still, if I think a prospective student will require much coaching on those basic ideas, I'll politely decline the student before that becomes a problem.
Tip for new players:
You need an obsessive personality. If music is simply an interest you'd like to add to your already crowded life, you can have a great time singing and playing with friends. On the other hand, if your goal is to stand out among musicians, be in demand for sessions and get the big hand for an instrumental break, you need to be obsessive. Very few "great ones" in any field are well balanced personalities. They do what they do pretty much to the exclusion of everything else and they do that not by design but because they can't help it.
Having a great time playing with friends,