As of today, Google is allowing developers to build free trial periods into their subscription apps.
Developers can now determine the length of the trial period on the Developer Console, and you can try the Play apps before committing to a purchase. In order to participate in the free trial, you must complete a full transaction through the regular billing flow. You won’t be charged until the trial ends, at which point payment is automatically initiated. You can cancel your subscriptions at any time.
Back in May, Google launched in-app subscriptions in the Play store that expanded monetization opportunities for mobile products. How to make money off apps is a persistent question within the technology community, perhaps people will actually begin to open their wallets after getting to try it for free.