Hi David,
In terms of membership subscriptions and access to premium content, content can be protected by roles and we have an add on product Site Membership Pro which handles the ecommerce for membership subscriptions and automation of granting or revoking the allowed roles to a user account.
However in terms of granting users their own blog or image gallery, please see the section "What mojoPortal is NOT Designed For" on our about page.
In addition to the security concerns that make it not recommended to give strangers edit access there is nothing built in to automatically provision a blog page or gallery page for a new user.
So this is not really a scenario that currently would be recommended for using mojoPortal.
Hope that helps,
Joe