You need a couple of generic stuff:

- A non-sanctioned country

- Partnering up with existing banks so you can actually process payments and manage fees

- Regulatory license for payment processing - if applicable

- PCIDSS compliance if you will process cards (can come later on, card schemes will knock your door)

- A really secure infrastructure and application (or you are in trouble)

- Some of the founding people actually knowing the domain

- Well-thought API

If you get past the first one then the rest is actually all about the investment.