In 2007, the former adult performer Mariah Milano returned to porn after a seven-year hiatus from the industry. A voluptuous brunette with a passing resemblance to "Millionaire Matchmaker’s" Patti Stanger, Milano shot her first adult film in 1998 when she was 18, appearing in 240 movies before retiring two years later. When she returned to porn in the mid-aughts, a co-worker approached Milano with a query she had never heard during her first few years in the industry: how much she charged as a private escort.

“At first I was like, ‘What? This is weird,’” says Milano, who retired for good in 2011. “But then girls would text me all the time being like, ‘Hey, Mariah, what’s your rate?’ I’d get hit up on Twitter, through email, asking how much. People were just assuming that I escorted.” Even her agent at the time, she says, approached her to see if she was interested.

When Milano first entered the industry, an adult performer openly escorting was relatively rare: “Escorts were considered dirty, bottom of the barrel. Nobody was open to admitting they did it.” Yet by the time she returned less than a decade later, the industry had changed drastically: the talent pool was larger, the number of available roles much smaller, and the advent of digital piracy had driven performers’ rates down. Escorting, or “working private,” has become one of the most lucrative ways for adult performers to supplement their flagging incomes, with many earning up to thousands of dollars for...