Prior to inviting people and creating any repositories, let's examine two important settings and set some defaults. Head over to the settings page and select the Member privileges tab:

As you can see, there are two settings. The first is about repository creation, and if enabled, any member of the organization will be able to create repositories under the organization namespace.

Enable this if you want to work more openly and disable it to be more strict. By disabling it, only owners will be able to create repositories. Outside collaborators (see the Difference between Members and Outside collaborators section) will not be able to create any repositories regardless of this option.

The other option is regarding the default repository permissions that organization members have on all repositories, new or old. You can choose from four options: None, Read, Write, and Admin. The None option is the least privileged one and it means that members can clone and pull public repositories...