When you're working on your own personal projects and you don't necessarily want them to be open source, it may be tempting to look into GitHub's private repositories.
GitHub charges a nominal fee for those repositories. Instead take a look at GitLab. GitLab is a great alternative to GitHub and best of all you can create unlimited private Git repositories for FREE.
Now, if you're interested in developing Open Source software with a massive community built around it, then GitHub is a perfect choice. But in my view, if you're looking for private repositories, you may not care are much about the community of open source developers on GitHub. Your team is just an invite away on GitLab.