I am aware that there are legal things that need to be considered if someone wants to start their own bank. However people earn money by selling on a website and people spend their money and transform it into digital currencies on the internet.

Lets say i start a simple website that allows people to pay money on that website and i give it back to them when they are ready to take it back (essentially storing money online). would that be illegal? might it be considered banking without a license or something? Or would that be perfectly fine?