It started with a Facebook "Friend" request.

"I was just, 'oh, he's cute, I'll accept him,'" a 22-year-old called "Nina" recalls.

She was 18 at the time, and didn't imagine that clicking "accept" would start her on a path to four years of prostitution across the country. "Nina" is a pseudonym; CNNMoney agreed to change the names of the victims in this article to protect their privacy.

Upper middle-class and college-bound, Nina had her plans derailed in her senior year of high school after her mother was sentenced to two years in prison for financial crimes. Lonely and looking online for male attention, she started messaging back and forth with a man who said he was falling for her. They talked about trips they'd take together as a couple, and about marriage, maybe kids.

"He sold me the biggest dream in the world," she says. "I thought he really did like me and we were going to live this fairy-tale life together.