I think you will start as a certain character that differs from all others in the game, and that you'll be the main person in the game too.
There'll be some stories that influence your maincharacter and from that I think he'll get involved with other persons who he works with/for.
Then he'll receive money with the tasks he does, but the tasks are not all legal and not everyone is pleased with it so you'll get enemies.
So then you have to buy all kind of stuff with the money you receive from the tasks to eliminate your enemies.
But that's just a wild guess, it would be more logic if in fact so it came to pass this i for him and your understanding