[2019] Another Co-Leader is charging new people to be in our Clan. And I am outraged! Also claims it comes with "mentoring" later. Should I contact Supercell?

hey, yeh this is very weird and definitely not ok to be advertising that stuff in-game.
unfortunately these things are very hard to trace/prove as they most likely occur outside of the game, but if you DM me their player tag we can take a look at the chat history to see if we can find anything there. thanks