react-native-iap is a great module to implement In-App purchases in your React Native App.
But react-native-iap will only provide you the client side code to implement IAP, you'll still have to develop a backend in order to validate the IOS/Android receipts and extract the purchases of the user.
... 50 hours trying to understand how to parse an Apple receipt
... 20 hours trying to understand how to parse an Android receipt
... 200 hours of DEV
... 5 hours explaining to your GF why you can't go out anymore
... and 42 coffees
You might have a backend validating your IAP. 😅
But you're still subject to potential errors without an extensive testing and you probably won't have other much needed features such as a dashboard to report real time analytics, a system to remotely update your products, a system to perform A/B testing... and many more tools that will help you increase your revenue.
If you feel like you should spend your precious time developing your app instead and (SPOILER ALERT) you definitely should.
You should definitely give a try at IAPHUB.
Using the React Native module react-native-iaphub you'll be able to process IAP on your app in no time!
And good news! If you're developing a new App and you have a tight budget, the FREE plan (which has all the features) should be enough until your app gains some traction.