Undercover policewoman dressed as a prostitute. From ho short form of whore, and 5-0 slang for police.
Girl walking up to car: Hey big boy, you want a good time?
Guy in car: Mos definitely, how much green you askin? I got a fitty right here girl...
Girl: Yeah? Well tonight's not your lucky night buster'cos I'm a cop and you're under arrest.
Guy: Damn ho 5-0!