title: Can I use non-renewing subscriptions for an app which offers a service, but has no free features?
body: <p>I want to write an app, which enables the user to calculate financial credit plans. The users will be professionals in the financial sector. The idea is that they pay for each month of usage, basically a subscription. The app will not have any free features, so the subscription does not "unlock" premium features, instead the subscription "unlocks" all functionality of the app.
  Can I use In-app non-renewable subscriptions for that? 
  Can someone point me to a good tutorial?</p>