John, what you're saying is accurate; what we cannot judge with any certainty is whether the OP's business model fits within the structure of the Enterprise model or the consumer model.
A website for the user to login and purchase a subscription plan for an iOS App, and then user logs in to the iOS App after purchasing a subscription is not a BUSINESS MODEL. It's simply one step of a bigger pipeline that, from its face, is little more than an effort to bypass paying Apple a commission.
Unfortunately, a forum like this is not very good for this task -- the OP's initial approach is not appropriate for helping him resolve his issue. Any answer to his question does not get him closer to a solution, because it's the wrong question.
If a business model was implied, it's simply, "How can I avoid paying Apple 30% of my sales?"
Everybody -- Apple, Google, and Microsoft (and more to come) -- all want a piece of the revenue streams generated from apps sold through their marketplaces. That has not kept businesses from making money that leverage mobile apps that don't make ANY sales through these platforms!
Thus, a better question is, Can this business model [explained below] support the distribution of free apps on the various app stores?
So the fact that there are already MANY businesses successfully selling services coupled to apps that are free IS the answer to his question, "does Apple take a 30% cut in [any given] scenario?".
Unfortunately, his next question is, "How?" Well, that's where the business model comes in. HINT: it's not built around cutting the marketplaces out of their commissions. His stated scenario (ie., business model) is simply insufficient to extrapolate anything from.