When you get Price's Crib, walk into the room that lets you save,change clothes, get cash, and get weapons. Go to the north wall to find three doors. Open the door on the left. The one on the right is the door you entered the room with, and the one in the middle cannot be opened. When you open the door, walk out a bit and turn left. Jump over the balcony and onto the roof. Make your way up the roof until you get to the peak. Turn left and you should see a chimney. Run over to it and press X to climb up. When you are on top you will see a soccer ball that you can kick to get it out.