How to Control Access to Your WordPress Site
You have a list of all the sites on your WordPress network; by default, other users cannot find other sites in the network. Unless you, the network admin, add such ability via plugins, a user cannot navigate from one child site to the next. The only list provided to a user is the Dashboard’s My Sites menu.
The My Sites page lists only sites the user is the administrator of, not sites on which the user has a lesser role. Additionally, the My Sites menu has a link for the user to create more sites (if the network admin has allowed it via the Settings menu in the Network Admin Dashboard).
Follow these steps to limit the number of sites your users can create:
Click the Network Admin link located at the top left of your Dashboard under My Sites.
Hover your mouse over the Plugins menu and click the Add New link.
The Install Plugins page on your Network Admin Dashboard opens.
In the Search field, type the name of the plugin, Limit Blogs per User.
Be sure that you have the Keyword option selected in the drop-down menu next to the search field, so WordPress knows to search by keywords (not by Author or Tag).
Click the Search Plugins button.
On the search results page, click the Install Now link for the Limit Blogs per User plugin by Brajesh Singh.
Click the Network Activate link on the Installing Plugin page.
The Limit Blogs per User plugin is now active on your network.
Click the Settings link in the Network Admin Dashboard
Scroll to the bottom of the Settings page to the Limit Blog Registrations per User heading and enter the number of sites that you want to limit your network users to.
The value of 1 allows users to create no more than 1 site, and so on. Additionally a value of 0, or leaving the field empty, allows users to create an unlimited number of sites in your network.
Be sure to click the Save Changes button at the bottom of the page in order to save all the settings you’ve configured.