UPDATE: THIS NEEDS TO BE DONE IN SINGLE PLAYER AND CAN NOT BE A PRO JOB
I'm going to show you an exploit on how to get unlimited experience/unlimited money and obtain all the weapons/mods in the game. First load up the map rats. This map will show up on the crime.net map when you are level 13. Play through the map until you reach "bus stop". Bus stop mission will require you to kill all of Mendoza's men on the bus. Kill all the men then head back to the
helicopter this will and the mission and you'll be rewarded with experience and money. When it says "payday" press a this will bring you up to three cards and you'll have to pick one of them. After picking a card it will give you a random item. When the item is shown press "start" then go down to "restart game". This will reload "bus stop"and you can keep farming experience, money, weapons,
and mods. When you reach level 50 go back to crime.net and look for the mission "rats"with three yellow stars.select the mission with the yellow stars And repeat the process until you are at level 100.