first of all i am not developer but i know some tricks which might help you to understand some basic tips of earning money by making app. www.thunkable.com is a platform where you can make some apps easily.
apps like tips or any sorts, you can earn money by showing some adds, there you will find plenty of functions to decorate a app, you can choose different functions if needed, by showing adds you can easily earn some money.
it never really hurts to try,so you can make app about something you are very good, or you can collect some data to organize a platform so users can enjoy and find this app useful.
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From @patrick.jane