I have developed an app that uses a proprietary algorithm to precisely calculate water needs for those who plan road races. Version 1.0 requires the user to input 4 parameters and the app provides 4 pieces of output. I offer a support link within the app. Future versions will have additional functionality, such as automated weather input (API) or additional features. The user-community is small (< 30,000) and would use the app annual, but seasonally (for example, the Boston Marathon).
What business model(s) are justifiable? Freemium will not work because the universe of users is too small to justify advertising. A paid model would provide limited gross income over the life of the app even if sold for $9.99. I would like to use a subscription model. I would prefer auto-renewable but a non-renewing subscription would also be acceptable. I am confused by requirements such as dynamic content, static content, and whether or not the app must retain some functionality if the subscriber chooses to unsubscribe to some IAP feature. Looking for clarity.