Most blogs start with a one-man operation. When you have a topic that you want to post, just talk about it in your blog. However, as your site begins to grow, there is simply not enough time for you to create as many content as you like. Also, if you need a new voice to your blog, its easier to find someone to do it than impersonate one.
This is when multi-author blogs are necessary. When hiring authors or setting up a guest post, you might want to give them their own account than give your own as they might compromise your site. But before you transform your blog into a multi-author blog, here are some things you must know first.
Read the tips here: http://www.wpexplorer.com/multi-author-blog-management/