Membership site solution?

I’m wondering if there are any ready-made solutions for this type of membership site. Here’s how I need the site to function.

Someone buys a membership and they are given access to an area where they can enter information. Let’s say it’s specific information about a person. The member who entered the information would be the only one with access to that information UNTIL… they decide they want to share it with someone.

At that point, they would be able to transmit the information from one or multiple specific records or entires to a third party, either via email or by giving them access via the website. The specific piece of information being made available to the third party would have to have a date and time stamp of when it was initially entered and by who.

I’m guessing this would have to be a custom build, but I’m not overly familiar with the membership plugins available.