You have a lot of options with your pricing. It's a tricky balance. If you are going for pure reach and relying solely on advertising for revenue, you can always offer a free publication, but if you also want to enforce that you have great content that has value, you may want to charge for subscriptions.
TypeEngine supports any subscription pricing or interval that Apple allows. According to Apple, subscription intervals can be 7 days, 1 month, 2 months, 3 months, 6 months, or 1 year. You can charge almost anything you like, subject to the store. For example, Apple allows choices within pricing tiers, starting at .99 and up.