Hit ~ to go to console mode, then type: cheat <cheat code> ,without the < or >, and hit enter to make it work. The cheat codes are:

loonies - Get.. another you?
alienprophets - Get fake cops
irissuxx - Message "Yeah!"
iwillmakethefamilyrich - Get 1 Lawyer
iwillripyourarmsoff - Get 1 Enforcer
youlittlehottieyou - Get 1 Seductress
pocketsfullofdough - Get 1 businessmean
yourliverlandedoverthere - Get 1 Bazooka guy
youhadbetterwearkevlar - Get 1 Blackwidow
trustmewithyourlife - Get 1 Bodyguard
ihavetenpoundfists - Get 1 Super Bouncer
likeatonofbricks - Get 1 bomber
youwillbestunned - Get 1 assassin
whatwasbrieflyyoursisnowmine - Get 1 thief
iwilltakecareofyou - Get 1 Big Momma
thegreatvassilizaitsev - Get 1 sniper
iknowodintoo - Get 1 ninja
kidiseeeverything - No fog of war
wowitsgreattobetheboss - God Mode
needmorelead - Get 1000 of everything
youbetterpay - Get 100000 cash