Membership site that protects the profile itself as private content

Hello.

I’m creating a site for which the content of the user profile is the protected content. In other words, the user profile with a host of custom fields that a customer creates via, say Profile Builder or something similar, gets used in a particular way for our deliverable. I do not want the average nonsubscriber to have access to the profile builder pages. I also wonder if it’s excessive or even impossible to require a double logon with the profile encapsulated by a membership program.

At the moment, I’m thinking of this workflow, although I don’t like it much:

1. Pay via PayPal.
2. Redirect to a complex url on my web site that is password-protected.
3. Somehow ensure that the password, which would be common to all users, is available by email or message (perhaps from PayPal or via PayPal Responder.
4. User creates profile and the business process completes from there.

Can anyone recommend a simpler protocol that doesn’t require two sets of logons (membership and profile)?

With gratitude,
Amy