Answer 1

Are you talking about for a website or for a mobile banking app?

With developers, you'll need to have a server that's hosting all of it. The server will need PHP installed on it, and will also need some sort of database that you'll be able to store/secure user accounts on. As for the resources required, a lot will depend upon the type of traffic being generated and the amount of customers really. As such, maybe using NodeJS would be better since its ability to scale is better, as well as its overall performance.

For the users, it'll be pretty minimal. They'll either simply need a browser, which doesn't require much resources, or they'll need to download an app onto their phone, which should work on nearly any smartphone today. Ideally, they should have the option of using either to ensure their ability to access their bank account with convenience.