Two player mode
Successfully complete the Burning Desire mission where you rescue Denise. A red two player free roam icon will now appear on Denise's porch near the door. The icon will appear there when she is home and will go on a date. Note: If both enter a car, the passenger will have free aim with a machine gun. Do not try to kill Denise, because you will never be able to date her again or play in two player mode at her house. Additionally, once you get your girlfriend, take her on a date. After you drop her off, there will be a rotating icon of two people directly in front of the door. Walk into it. It will tell you to push any button on the controller two. Do so to start two player mode, involving CJ and his girlfriend in a free roam.

For more fun in two player mode, start the two player mission. Then, enable the "Spawn Jetpack" code and remove the Jetpack. Then, have player two get the Jetpack. Enable the Jetpack code again, then have player one get it. Both players can now fly around and do the two player missions this way.

Two player mode in Los Santos
Note: You must have a second controller inserted in port two. In the Ganton area, start from Grove Street where the Johnson house is located. Drive under the first bridge and continue to go straight. Next, youshould drive over some railroad tracks. After this, you should drive under a second bridge. Take the first right turn you see. It should be a dead end. Drive until your car hits the grass, then look to your left. You should see an open doorway. Walk through it and you should see a small "2 Player" icon. Press any button on controller two to begin. Additionally, when you are on the missions from Big Smoke go north of his house. You should see some wrecked buildings. Go through them to find a two player free roam icon.

Two player mode in San Fierro
Not far from the garage you own and beyond the construction area is a large building with a parking lot on either side, on the right side (north according to the map) is a two player icon. Multiple people types can be selected by the second player (three women and three men). Unlike those from the dating missions, this two player location will never go away.

Two player mode in Bone County
Starting at the abandoned airstrip, go west and north onto the road. There is a blackish-brown building on the south side of the road with a large balcony going all the way around it. Follow the balcony half way around and you will find a two player mode icon.

Two player mode in Tierra Robada
Start at your safe house in El Quebrados. Get on the street and follow it a short distance south until it turns left around the corner of a building. On the south side of this building will be a two player free roam icon.

Two player mode in Whetstone
Go to the General Store in Dilmore. There is a two player icon there. The second player will be able to change their character.