Audio Streaming app - in app purchases

I understand 'Reader apps' can use their own payment mechanism i.e Stripe etc, but the user has to have previously subscribed to the content.? I have an app that provides virtual tours to users and users can purchase these tours within the app, do i need to integrate in-app purchases.? The user can consume the audio only with the app.

Audio Streaming app - in app purchases
 
 
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