Thanks.
Okay, my ideal scenario as follows;
there are two user groups, lets call them diners and cooks. To become a cook, a diner has to pay a subscription. Once the user is a cook, if they join a group owned by Admin, they automatically become a moderator, but not if they join any groups owned by diners. If diners join the group they are not moderators, and there fore cannot create events in the group, which is the crucial thing here. If the cooks subscription expires they become a diner again and are no longer moderators.