What is the correct approach to use chatgpt and API on app with billed services

hello. im building an android application that with use chatgpt services and i want to have ads or subscription but i dont know what is the correct approach on how to pay chatgpt. is there a way to have every client that pays the app have a personal api key to be used in my app? should i have a api paid for all of my clients? im not sure the correct approach please guide me, thanks

Hi and welcome to the Developer Forum!

The two most common types of customer billing is fixed monthly tiered and per token, you charge your clients a rate which you make sure can cover your costs plus some profit margin, and then pay for your API usage from that.