A shortage of affordable housing is partially to blame for a number of ads offering discounted or free rent in exchange for sex, an advocate says.

Many tenants and landlords use sites like Craigslist to communicate, but some online ads aren't looking for money in exchange for shelter.

There are several ads in the "rooms & shares" section offering "free rent" to attractive women, in exchange for "discreet and mutual arrangements."

"Seeking an attractive, fit and classy female, 19+," one ad reads.

"Busy good looking and young professional, recently single, just trying something new and different and straightforward."

Another poster wrote that they are looking for a "sexy roommate," who is open-minded, loves to laugh and will do some house cleaning.

A third promises free rent for the "right girl," from a man who describes himself as attractive and in his mid-30s.

"Let's drink tonight and see if we can make this work," the ad says.

While the ads aren't a new concept, they take on a more sinister tone in a city with high rental rates and low availability.

"They seek women that are the most vulnerable," Maria Paredes told CTV News on Friday.

Paredes, a transition house worker for Vancouver Rape Relief and Women's Shelter, said that women are forced into accepting the deals when they can't find an alternative.

"It's really despicable to know that men are taking advantage of women's poverty and the current affordable housing crisis here in Vancouver," she said.

While Parades says the ads are essentially soliciting prostitution, police say their hands are tied.

"For the most part, these ads aren't illegal. The wording in them is left very general for a reason," Vancouver Police Const. Brian Montague said.

"Obviously it's implied that there's an exchange of sex for services -- in this case free rent -- but that's an assumption and we can't arrest people based on assumptions."

Police said the ads are no different than those for "sugar daddies," which openly invite women to find wealthy benefactors.

Montague added that police have to prioritize where they place their limited resources, and because the rental agreements are generally between "two consenting adults," officers spend their time investigating other cases.

"It doesn't mean they can't become a priority if public safety is a concern or if there's a specific ad or a person that's taking advantage or exploiting someone," he said.

Although officers are generally unable to press charges, police warned that women should think twice about responding to ads offering free rent online.

"Some of them are individuals who would be predatory, potentially suffering from mental health issues... Things can go very bad very quickly," Montague said.

While advocates want more support from police, they also think that political leaders have a role to play.

At the Vancouver Rape Relief and Women's Shelter, Paredes said she's seen how women in transition housing struggle to find homes.

"Welfare rates are extremely low, housing rates are extremely high, and women always tell us how hard it is to be out there looking for housing."

Paredes said that it is "terrifying" to her to see that women aren't being protected by the criminal justice system, particularly in cases of spousal abuse.

"They have a responsibility to women to have affordable housing and to have real options and resources for them to leave their abusive husbands or really survive in this city."

Anyone in need of assistance can contact the Vancouver Rape Relief crisis line or learn about transition housing by calling 604-872-8212.

With a report from CTV Vancouver's Penny Daflos