Pro Sites Appears in Sub Sites

Hi all,
I enabled Pro Sites so that I could configure my Mu site to be able to charge sub site users for the service.
But when the Pro Sites plugin is enabled each of the sub site admins see: "create your service interface" as if they have to now create their own Pro Sites configuration, or is this a prompt for them to now pay for their subsite?
Also, how can I enable Pro Sites to work without bothering sub sites I have already created that don't need Pro Site subscription / payment?