'John' is 60, divorced, and gets paid to have sex with prostitutes. Well, "more often than not it’s just a handjob" he says.

He is one of several private investigators being hired in Australia as 'brothel busters', who pose as regular customers in order to unearth illegal sex work.

"I'm pretty sure plenty of fellas would be a bit envious of how I'm earning a bit of pocket money from time to time," he told news.com.au, replying when asked whether it was a good retirement gig: "Oh, most definitely."

His job is necessary because authorities have little power to access premises without a court order, making it difficult to bust the brothels posing as massage parlours that are ubiquitous in New South Wales.

John can provide them with highly graphic detail about the services on offer however, filing reports that can run for up to three pages and include dates, times, people, places, who, what, when, where and how much.

"It’s a document that will be used in court, so it has to be pretty detailed and very accurate. It’s not something you can waddle off in a couple of minutes," he said.

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More often than not, he claims, the parlours are fronts.

"If you looked hard enough, you might be able to find a massage parlour that doesn’t offer sexual services," he said. "In my experience there have only been three premises where I have gone in and not been offered that service some time during the course of the treatment."

John notes that while some offer intercourse which he obligingly accepts, "more often than not it’s just a handjob. They just want to get it over and done with and get the next one in."

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Lachlan Jarvis, managing director of private investigation firm Lyonswood, is in charge of hiring undercover sex investigators.

"We prefer people who are single, and obviously they have to be willing to undertake sexual activity," he told news.com.au.

"I’m not surprised that some people would say that spending ratepayers’ money on the services we provide is outrageous, but they don’t understand that we help stop sex trafficking, for example."

John counts himself lucky to have what is a fairly relaxed and flexible job.