Army of TWO The Devils Cartel

To gain access to all outfits you have to beat the game one time to unlock Insane and after that again on insane. Also you need to reach rank 25, which should be no problem by playing the story twice. Overall it will cost you 161.000$.

There are a total of 19 Outfits (Tactical Gears) in the armory. Two of them (Alpha & Bravo) are accessable from the start. Another 12 are avaible for purchase right from the beginning for 3.000$ each but you need a certain rank to buy them.

Four will be unlocked while reaching rank 25.
Salem (20.000$)
Meat Shield (10.000$)
Rios (20.000$)
Executiv Rios (25.000$)

The last one will be unlocked when you beat the story on Insane:
Inmate (50.000$)

The achievement should pop a second after you bought the last one.
If you find any mistake feel free to leave a comment.

I think I have found out the best way to grind money, if you don´t have the Outside Contact - Overkillers like me.
Go to Outside contact -> Level 16 "Suicde Run". Difficulty Insane for max Difficulty Money Bonus.

Trivia: All you have to do in this short section is to drive a Car to a Destination. It isn´t possible to die in this level.
- Choose to drive - the AI shoots. You should do this because the AI will do higher combos on the MG.
- Drive as fast as possible. Avoid obstacles like the MMG cars and push the whole time the RT (driving) button down.
- If you have finished the level don´t use "skip" (the back button) in the menu/level stats. Choose-> "next" (A button) until you are on page 4 -> then quit (to main menu). Because otherwise the game will force you to do level 17. So you have 2 loading screens instead one loading screen. To do Level 16 again you will have to go to the main menu anyway.

What you have to keep in mind:
You will get the most money in this section if you score high combos. So overdrive as many enemies as possible. The best Combo possibility is on the end section of this level. -> In the last turn before you drive downhill it is possible to overdrive 5-6 enemies, if you hit all of them and on the downhill section another 6-8 you should get a very high bonus. Aim for the gate directly before the MMG in the end because sometimes 2 enemies run 1 secound before the cutscene starts onwards you -> 2 more kills for your last combo.
Another nice section for combos is before the big plaza. There are many enemies but most important: If you stay on the right side directly before the plaza you can hit 4 Enemies at once.
Here are my datas: In my first trys I was poor and could only achieve 3200$ with a time of 2:02. After a few tries and knowing the "course" I knew where I could do combos. So I have managed it to get constant 4200-5200$ in 1:32-1:40 minutes. Because of the shortness and high reward, this Level has the highest effiency in the whole game for farming gold.

I know this sounds (and is) boring. But even if you do this for only one hour you should earn around 100.000$ (loading times eat some time too)
Too compare: I have played the whole game through on Normal and Insane and had only earned for 2 complete playthroughs around 500.000-550.000$..