> Assuming I have enough capital and already has the license from the local central bank,
Do you though? That's the hard part, not:
> how do I go about building the MVP? The MVP that I have in mind is a simple mobile app where users can: - Transfer and receive money - Pay bills
Look up Railsbank for their API if you are in the UK.
There is a startup in The Netherlands that did exactly this, they are called 'Bunq'[0]. A while back a book has been published how they did this, it is, sadly enough, in Dutch[1]. One of the things that comes clear thanks to the book is that Bunq never wanted to use an additional banking API like another user here said. They wanted their own banking license and not use any kind of gateway via one of the 'old' dinosaur banks.
0: https://www.bunq.com/ 1: https://www.bol.com/nl/f/breken-met-banken/9200000057850318/