Would we be successful? It's been done in real life, but the perpetrators have been caught, because they didn't have the savvy or the skill that Niko, Lopez, or any of the other protagonists had. This doesn't mean that all who copied the crime would be doomed to failure.
Let's begin with something basic, for starters...
In all GTA games, it is randomly possible to earn money by provoking people into fights and then beating them. You only get a few dollars from most of them, with some of them dropping several bunches of dollar notes, so you'd have to go around different Burroughs and alleys, picking out many targets, if you want to make a fair amount.
How would you do it? How successful do you think you would be if you were to do it?