After completing the first UP mission and receiving Ewan, talk to him about the Winch challenge. After completing level 3 on this challenge, bet the maximum amount of money. Even though you have already done this, the height does not raise. Therefore you can continue betting at the maximum amount. After about four times (depending on how much you start with), you should have about $7.0 million. You can continue from here in order to get the maximum wager amount to $5.0 million (when you have about $14.0 million in funds). From there you can repeat this as often as desired when you need money.
Note: To save time, if you are trying to use the above method to increase your money, use stackable items from outside of your stronghold. For example, try the gas canisters across the road (or for something less volatile, use the shipping containers directly across the lake behind your house). Items used from outside of your stronghold stay in the exact location you put them until you quit your game, giving you a prepared stack height the next time around. Two or three attempts may be required to gather the items, but it is well worth it, as once done it requires only seconds to win the challenge.
Unlock Extra Costumes
Each of the character in game has 5 costumes. To unlock them You'll ahve to beat Fiona's level 3 challenges: Gun Emplacements, Pistol, Grenade Launcher and Sniper.
Free Vehicle Repair and Rearming
Do you have a vehicle that needs repairing or more ammo!? You can get both for free by entering any allied HQ or outpost, you don't need to buy anything or even take a contract, just leave. Once you leave, your vehicle is fully repaired and rearmed waiting for you outside.
Winning Challenges Easily
Bet the maximum money for the level 1 and 2 challenges then save and reload the game until you win. Bet the minimum money for the level 3 challenge.
When Carmona's men are attacking the PMC, after you destroy the tanks set a charge of C4 on the gates closer to the mansion and blow it. It should drop straight down and block the road leading out of the compound. Enter the mansion and trigger the intermission sequence. When you exit the building, the road leading out of the compound is still blocked. Kill Carmona's bodyguards and his jeep should be stuck on the rubble of the archway. Kill him and snap the picture for easy verification of Carmona.
When completing the mission on the oil rig in the water behind the PMC, kill Blanco and take his weapon, the hunting pistol. The hunting pistol is a very powerful weapon, often killing enemies in one shot. With the hunting pistol in your possession, continue through the "Finding Solano" mission/ After the encounter with Carmona inside the villa, he runs in a straight line directly away from you, giving you a clear shot at his back. If you miss on the first shot, he has a good bit of a jog until he reaches his jeep, giving you plenty of time to gun him down.
Sniper Rifle Scope on Regular Rifle
Have a sniper rifle in your inventory. While you are using the scope, press D-pad Right to switch weapons. You should have an assault rifle out while having the scoped view.
Capturing Outposts Quickly
When playing in Co-op mode with a friend, look in the same direction at the same time. Throw the signal smoke to call in for reinforcements to capture an outpost. If done correctly, both of the thrown signal smokes will start to smoke and two helicopters will appear. This will speed up the process when you are getting shot or are in a tight situation.
Stealing Fuel Without Upsetting a Faction
This is most useful when used with factions who are already hostile (to keep them from shooting you down), but can also be used to keep friendly factions from becoming upset with you. Obtain one of the helicopters used by the faction you want to steal from (or one of its allies), and allow your disguise to finish. Fly to the location of the fuel you want to obtain and lower your winch. Grab the fuel tank and lift off before the enemy soldiers recognize you, then fly to a secure location (either the PMC or a remote, open location). Once out of sight, call Ewan in for the pick-up. Note: Using a heavier helicopter is recommended, as the Rogue and Gunney class choppers are extremely difficult to control when carrying a heavy fuel tank. Also, there are at least half a dozen fuel tanks relatively close to the PMC, most of which are controlled by Universal Petroleum. Spending the fuel for an Ambassador Gunship (an Allied helicopter, who are allies with UP) is well worth it if you are going to use your PMC as a fuel depot.
Use the following trick to steal fuel from a friendly faction without having to worry about affecting their status towards you. Go to an outpost that has fuel tanks and tag them. Then call in Ewan for the extraction. If a soldier happens to call in a report about your hostile act, go inside the outpost to cancel the call. By doing this you will get fuel and the faction will still be friendly with you.
This trick requires a fast vehicle (for example, a sports motorcycle). Find an outpost that has a fuel tank. Look for an easy way out before you attempt to steal the fuel. Once your vehicle is positioned facing the fast exit and after making sure no one sees you, tag the fuel tank and call Ewan for extraction. Run to your vehicle and drive as fast as you can until you are far enough from the place so that no one can report you. Note: This also works with a helicopter as your vehicle when you are in the jungle area, but requires more time because you must wait a few seconds before you can lift off.