OK,
Sounds like you are being asked to reinvent the wheel here.
You can use a database to manage users/groups. Depending on what group you are in and what user you are determines the content you have access to.
But I think your current path is a wild goose chase. This stuff already exists and does not take much to customize.
What you are looking to build sounds somewhat like an affiliate or groupware system.
My advice is get a copy of VM Ware, browse their
virtual appliances and start with a turnkey solution that can be customized.
Try
Redmine? Open source,