The "Airbnb for cars" is getting serious.

Car Next Door quietly launched in Brisbane in December. It’s a peer-to-peer car-sharing platform that allows people to rent out their car by the day or hour.

Now, to encourage uptake, the online start-up has launched a new valet service. To save car owners going to the Department of Transport and Main Roads to change their registration – which everyone can agree, is the pits – Car Next Door will send a screened, trusted valet to stand in line and do the paperwork for you.

Applications from car owners to rent out their car have doubled since the new valet service was introduced. “Brisbane people are paying a lot for their cars,” CEO and Car Next Door co-founder Will Davies says. “A lot [of cars] are sitting around doing nothing, so this is a good way of offsetting the costs of owning a car and making a few bucks out of it.”

Since launching in 2012, the platform has attracted around 1000 cars and 37,000 borrowers in Sydney, Melbourne and Brisbane. After Sydney, Brisbane has the second-highest transport costs in Australia. Davies says he’s impressed with the demand for the service in the Queensland capital. “We’re really encouraged by the usage [in Brisbane],” he says, “because a big concern for us is [you might] get a whole bunch of cars but there’s no actual demand.

“The average owner on the platform, who makes their car reasonably available, is earning an extra $3500 a year through it,” he continues. “And that’s after paying extra fuel, wear-and-tear and stuff. So that’s a real figure.”

Davies reckons there is plenty more room for extra growth and hopes to achieve a goal of having a car within a five-minute walk of anyone in a major city. He hopes to launch Car Next Door in Adelaide, Canberra and Perth in the future.