Army of Two: The 40th Day

This achievement is an accumilation of wealth throughout the entire game. You don't have to have a million on you to get it, the money you spend will go towards it. I managed to get this achievement towards the end of my first play through on normal difficulty.

Ok just like CyberChristFF said in the above solution, this achievement is accumilation so you do not have to have it all at once.. If you dont have this achievement by the end of your first playthrough here is a pretty good way of making money fast.. go to chapter select and choose Chapter 6, act 2, - Sink it, and put the difficulty to casual.. once you start there should be a case directly infront of you about 20feet or so and 2 guys guarding it, one to the left behind some crates and one to the right just standing around.. what i do is put my partner to aggresive regroup stance and run to the case and collect the 42,500$ then kill whats left of the guys.. once you have done that, step jump the security checkpoint gate, unlock the door for your partner and continue along the mission.. as soon as you go through the door you should get an objective to destroy the AA guns so the chopper can land.. once you destroy the ship you will get a checkpoint..
Dosent take long at all my best run through was 2minutes. Rinse and Repeat and you should have the achievement in no time! I hope i could help!!!!....