Q - How important is a platform when writing for Christian periodicals?
A - Where having a platform is becoming more and more necessary if you are writing nonfiction books, it really is not necessary for writing articles--although it could only help. Depending on what topic you are writing about, the editor does expect you to have some sort of credentials to write on the particular topic. That does not necessarily mean a college degree, but is more likely tied to your experience. For example, if you are writing on marrage or family issues, they would expect you to have been married for a good length of time or to have raised children. If you are are writing on theological issues, they may expect you to have a degree in theology or to be a pastor.
Writing on your topic for periodicals is actually a great way to start developing the platform you will need for selling a book. You want to do everything you can to see that your name is ultimately linked to the topic you write about. One of the best ways to do that is to write on your topic for as many different publications as possible. You want to become know as an "expert" on your topic.