User Profile

Our app's main purpose is to allow users to upgrade their accounts and become analysts. After becoming an analyst, users can create their subscription plans for other users. Another user can then subscribe to their plan, gaining access to all the signals and tips posted by the analyst. This way, analysts can earn money. So, my question is, for upgrading a normal user to an analyst, should I use in-app purchases or a third-party payment gateway? When the analyst creates their plan and users can pay to subscribe to the analyst's plan, should I use in-app purchases or a third-party payment gateway? As I've checked other similar apps for my app scenario, a third-party payment gateway seems suitable because in our case, we are not unlocking any functionality. Users are paying the analyst for their service. Please help me decide what I should do so that Apple approves my app on the first attempt."