Go to City Wok. There will be two elf kids in front of the store. Attack them with X. This is one of the best places to farm for XP and money since there are only two enemies. XP is given out evenly no matter how many enemies there are. When the fight is over, walk into City Wok, then walk back out and the kids should respawn again. Repeat this as many times as desired. You can sell your loot at Jimbo’s Guns. You can also obtain one of the best weapons in the game at this shop, the Level 14 “Sweet Katana”.
Note: If the kids do not respawn, walk into City Wok until you see the save sign in the bottom right corner. Additionally, be sure to pick up the loot the enemies drop. If the loot accumulates too much, the kids will not respawn. Enemy loot is how you obtain the majority of your money in South Park.