Apologies if this is not a correct space to ask the question but I have been really struggling to get the answer on that.
Basically, I know that for applications there are four most common billing models: One-time charges, Recurring charges (mostly used for paid apps), Usage based charges and Application credit. Obviously, combination of models is possible.
My main question is: What parameters may be tracked and taken as a base for charging model? What are the formal requirements that need to be met so that the final charge is calculated?
Does anyone know if there is any detail guidance / official procedure re billing models?