WHEN there's a knock on Marlene Hetaraka and Remi Delomel's door it could be someone from Japan. Or Germany. Or America.
The young St Kilda couple are among a growing number of Australians who use Airbnb, an online service that helps people rent out spare rooms and entire homes to travellers. More than 2300 Australian homes are listed on the international site, including about 400 in Melbourne.
The website has turned the couple's home into a bed-and-breakfast - albeit a relaxed one with no doilies - and since joining in October, 14 tourists from around the world have stayed in their sunny spare room.
''I'm getting married at the end of the year and have a mortgage so it's helpful,'' says Ms Hetaraka, a fashion designer. ''It wouldn't suit to have a long-term person. Being a couple, this suits our lifestyle.''
For $75 a night, guests are given a key to the two-bedroom apartment, which is a stone's throw from Acland Street.
''We aren't noise-sensitive. You don't have to be home before 1am. The only rule is close the balcony door,'' she says.
Guests are given a list of things to do, a bicycle, linen, high-speed wireless and complementary toast, jams, tea and coffee. Despite initial reservations about sharing their home with strangers, the couple are now comfortable with the idea.
''It requires a lot of trust, from both the host and the guest,'' Mr Delomel says. ''But we are used to it, it keeps the house clean because guests are around.''
He says tourists who use Airbnb get an authentic travel experience that differs from a hotel or hostel. It's also cheaper.
Belgian sisters Ciska, 22, and Florentien Van Keerberghen, 17, are the latest to stay in the apartment. ''It's a lot more personal,'' Ciska says. ''You get information from locals, like how the tram works, how to get to the airport, the nice places to eat.''
The site was founded by Joe Gebbia and Brian Chesky in San Francisco in 2008 and is now valued at about $1.3 billion. It offers accommodation in 192 countries and charges a fee for every reservation. Travellers search for accommodation, send a message to their prospective host and then pay for the room with PayPal or credit card. The payment is delivered to the host 24 hours after check-in. Bad behaviour is curbed by a review and ratings system.
After an incident in San Francisco last June in which an apartment was ransacked and vandalised by a guest, Airbnb introduced a $50,000 insurance guarantee, a 24-hour hotline and a taskforce that investigates suspicious activity.
Australia's peak bed-and-breakfast industry association is concerned about the lack of regulations governing Airbnb.
''Our members jump through so many hoops and council regulations,'' Hosted Accommodation Australia national chairman Ciaran Cryan says. ''We know we have a good product to sell, we are responsible operators, whereas this is a website for everyone and anyone.'' He also raised concerns about landlords not taking out public liability insurance and subletting rented properties without consent.
The Australian Hotel Association's Victorian branch had not heard of Airbnb. But its general manager of tourism accommodation, Darryl Washington, says there is a role for all sorts of tourist accommodation- as long as fire, health and public safety standards are met.