14-year-old Stephanie runs away from her home in the Pittsburgh suburbs to become a model in NYC. She has $9 in her pocket when she's "rescued" by a daddy (pimp), whom she immediately adores like a nun loves a pope she has sex with and for.
Stephanie is incredibly naive, but maybe that's the 1970s for you? This is a first golden age of young adult fiction gem that popped into my head. I internet searched it, and lo and behold it is available for loan from the Internet Archive. nb: even if you download it, the book isn't really downloaded, just full-text accessible, so beware before hopping on the subway thinking you're going to read it when you have no connectivity.
It's kind of whacked that there's zero reference to race/ethnicity, and don't even get me started on the kindly cop.