Pro Sites: Where is the Pay to Blog option enforced?

I have the Domain Mapping and Pro Sites plugins loaded and am trying to work through issues one at a time, but still have a couple of issues with it:

(1) If I tick the Pay to Blog option, and set the page and post quotas to 5 each, when does this take effect? On the required FREE level? Does it apply on Trials too?

(2) I really didn't even want a free level, so I hoped the Pay to Blog feature would take them to the trial and then limit the pages and posts as I set the limits in the config. Is this they way it works? If not, what is the designed work flow, or customer flow as it were?

Thanks -