treat her like a prostitute
The title of a Slick Rick song, the phrase was coined by Ricky D himself, used to describe the reluctance men should take toward women when getting involved with them. After the popularity of Rick's song with the same title, this phrase became popular.
"Treat her like a prostitute, don't treat the girly well until you're sure it's sweet." -Slick Rick, "Treat Her Like a Prostitute"