You can create a simple Joomla membership site with Joomla core components. Simply do the following:
1. Creating users can be done in two methods:
a. Admin assigns the user and password. In this case you have to disallow user registration at the Global Configuration - System - Users Settings.
b. If you wan users to register themselves go the Global Configuration - System - Users Settings and allow registration.
A confirmation link will be sent to the registrats email.
2. For users to be able to login enable 'mod_login'. You can assing redirect link when the user is signed in and signed out.
. Assign the menu link to be 'Registered' as image below

Only registerd users can go here. If they are not logged in a warning message will show up.
3. Super Admins can manage users by going to Control Panel - Users Manager. Super Admins can create, delete or edit users here.
Simple as 1-2-3! Your membership site is setup! If you want to sell memberships you will have to purchase some commercial extensions but this is good enough...






