Press both L + R simultaneously to call up a cheat interface. Enter these cheats there.

MIDAS - Unlocks 2 Player mode.
FREEALL - All items cost nothing (doesn't apply to services).
PARTY M - Unlocks Party Motel in 2 Player Mode.
SIMS - Unlocks Play The Sims Mode
FISH EYE - Unlocks first person view (press BLACK).