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Does the guy who suggested it have any idea of the legislation and regulation involved?
What about gaining customers, do you have a reputation that would make people trust you with their money?
I would spend no more time on this, I can say with 100% conviction that if this is a new idea to you then you have no chance of getting it off the ground.
A friend of ours worth many millions says I should start an online Bank!
Perhaps you should start with something smaller - like a service to rival PayPal - and then graduate to offer additional banking services.
PayPal needs some good competition. Best of luck.