After CJ kills Big Smoke and knocks Tenpenny to the ground. CJ became rich due to his garage holdings in San Fierro and half of his fortune at the Four Dragons Casino in Las Venturas. And his contract with Maddog as his manager. He decided to leave his formely life in the ghetto and gang wars to back to Liberty City to start a new life and start bussiness there. In his big and luxurious crib with swimming pool.and two new sports cars.
The period that cj lived in Liberty City is October 2001 (this explains the lack of water in the swimming pool), the same period as the events of GTA3. He is 33 years old after living in San Andreas for 9 years.
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