Massage parlours offering sexual services are not hard to find.
There are online adult forums, where clients leave comments and write reviews of their experiences.
There are community websites and forums, where some massage businesses openly post ads seeking "ladies" and gay men who can massage and provide so-called "extra" services.
Joy is a Thai masseuse in her 30s who has worked at several massage parlours in Sydney for about a year, but her name and voice have been changed to protect her identity.
She is in Australia on a student visa, studying English and accounting, and works at parlours that masquerade as straightforward massage parlours.
(Thai, then translated:) "When I was in Thailand, I never thought I would end up offering dodgy massage. When I first started working as a masseuse, I was actually surprised to know that this kind of service existed. But after so many clients asked me, I thought to myself, 'Okay, I'll do it,' because I get a lot of money and it is less tiring than normal massage."
The business owner usually pays Joy the equivalent of half the fee for a standard massage.
Any "extra services" are negotiated directly with the clients.
The fees for the extra services, such as nude massage, masturbation, oral sex or intercourse, range from $20 to $150, and Joy can keep the full amount.
She says, on average, she can earn around $1,500 to $1,700 a week in cash.
And she says the business owners benefit from the extra bookings brought in by masseuses who offer sexual services so they often ignore such transactions on their premises.
Dr Helen Pringle, a senior lecturer in social sciences at the University of New South Wales, has a particular academic interest in human trafficking and sexual slavery.
She says the massage business often involves a grey area.
"There'll be legitimate massage, or ordinary massage, that is offered, but, also, there is a possibility of 'happy ending.' Often, the employers will hire people to do massage but say, 'Look, you know, if you want a little bit of extra money, you can do happy ending.' It's kind of not usually penetrative sex, in the usual sense of prostitution. So this is kind of a grey area that a lot of massage parlours operate in, between normal, ordinary massage and brothels. A lot of workers in that grey area feel pressured to provide extra services in that way."
Ann's name and voice have also been changed.
A massage business owner from Melbourne, Ann explains there are three main types of massage parlours in Australia.
(Thai, then translated:) "The first type is 'out-in-the-open' massage shops, whose owners tell their clients about available sexual services and advertise new staff. The second type is 'one-eye-closed' massage shops, whose owners pretend these sexual services are not available, yet allow their staff to offer them. The final type is 'hidden' massage shops, whose owners declare that there are no sexual services available yet individual staff might offer them secretly."
It is not illegal to sell sex in most of Australia, but prostitution laws differ from state to state, enforced by a state authority, local councils or the police.
Unlicensed brothels are difficult to monitor when it comes to sexual-health practices or workplace health and safety.
Joy says the places she has worked have never required or encouraged her to get checked for sexually transmitted infections.
(Thai, then translated:) "It's up to me to get checked or not. When I first came here, a friend told me to get checked. So I get checked every six months."
She is adamant she is not a victim of human trafficking or sexual slavery, though, and says she does not know of any others who might be.
(Thai, then translated:) "I never heard of it. All of my friends who do this type of job are willing to do it at their own free will, because they can earn a lot more money than other typical jobs."
But Dr Pringle has a different view.
"They (workers) define trafficking in a very narrow way, as being kidnapped and/or being chained to beds, or being held virtually hostage. But both the international trafficking protocol and, also, Australian law on trafficking, you don't have to be forced in order to fall into the category of trafficking. So the provisions in Australia at the Commonwealth level talk about whether the employer is reckless, whether the employee will be exploited. So I would say that the key problem is exploitation, rather than the movement across borders or that kind of movement in trafficking."
Dr Pringle wants Australia to adopt the Nordic model of prostitution policy.
Under it, sex work is decriminalised but buying sex is a criminal offence, so the law penalises the customer, not the sex worker.
In the short term, she suggests a special police unit like Sweden's, where women can bring their complaints, problems and questions in confidence.