For two years, Steve Gutmann found a way to make a little extra cash. His house sits in Southeast Portland’s Richmond neighborhood, two blocks from Hawthorne Boulevard. He knows parking is a valuable asset in Portland. So he’s rented out his driveway.

His first renter was a New York City transplant living downtown who was willing to rent Gutmann's driveway to avoid paying higher parking fees elsewhere. Gutmann parked his car on the street.

“I was making enough to take my family out to dinner once a month just to give up my driveway,” Gutmann says. “So that seemed like a good tradeoff for me.”

In the sharing economy, we've opened our bedrooms, loaned our bikes and held open our car doors to strangers. The driveway was inevitable. Gutmann advertises his driveway on JustPark, which has been around for years.

Now, two homegrown startups—Citifyd and Parkzilla—will offer apps their creators hope will greatly expand the number of Portlanders who rent out their driveways.

But there's a familiar problem: Renting out your driveway can be illegal. Most homes in Portland are zoned as residential lots, and city rules forbid commercial parking on them.

"There's no way that it could currently happen legally," says Jill Grenda, a supervising planner at the city's Bureau of Development Services. "It would take a code change."

With parking apps, the city is faced with the same regulatory dilemma posed by sharing-economy giants Uber and Airbnb: Either crack down on sharing-economy businesses that violate city codes, rewrite the rules, or just ignore the situation. 

Portland's response to Airbnb and Uber shows how City Hall has struggled—and eventually bowed to pressure and demand—when it comes to sharing apps.

The City Council rewrote the rules last summer to allow short-term rentals such as those posted on Airbnb. The new rules require hosts to get licenses and undergo safety inspections, and require Airbnb to collect lodging taxes.

But the city's enforcement has been spotty at best. It took the city nine months to crack down on rental sites that weren't registering to pay taxes. (It hit one short-term rental company with a $3,000 fine last month.)

Regulators have also yet to address the estimated 94 percent of Airbnb hosts who haven't bothered to get city permits or undergo safety inspections. (Mayor Charlie Hales said last week more hosts would seek permits if the city reduced the $180 fee.)

Portland's ban on Uber and other ride-hailing companies ended April 21, when the City Council approved a four-month test period that deregulates for-hire transportation before creating any permanent rules.

Citifyd, Parkzilla and other parking apps pose the same problem Airbnb did: neighbors who object to houses on their street running a business.

"When this zoning code was written, nobody ever imagined that something like that would even be possible," Grenda says. "Our code is still trying to catch up."

Neither of the new parking apps have hosts signed up yet. Tim Ashman, 50, is the one-man show behind Parkzilla, which launched quietly last week. Ashman has worked most of his career in IT and came up with the idea during a shopping trip in the summer of 2013.

"I was down in the Pearl with my girlfriend, and you're doing that circle thing," Ashman says. "I'm passing all these driveways, and no one's home, and I'm like, 'Man, why can't I just park right there? Why can't I do that?'"

His app connects drivers looking for parking spaces with homeowners or businesses offering rentals on an hourly, daily or monthly basis.

"Hopefully, people see it as a VIP thing," Ashman says. "Most people I've talked to are willing to pay three, four, five bucks to park if they could schedule it ahead of time, roll in with their girlfriend, park, bam."

Sohrab Vossoughi, founder of Ziba Design, decided to create Citifyd after having to park 16 blocks away from Providence Park for a Portland Timbers match.

"You think about Division Street," Vossoughi says. "All this stuff that is going up without any parking spaces being built and commercial areas that are expanding. First Thursday. Last Thursday. Hawthorne [Boulevard]. There's always something going on in the city of Portland where you need parking."

As the Portland Business Journal reported last week, Citifyd has $1.1 million in funding from Ziba, angel investors and Vossoughi himself. It's currently in beta testing and is scheduled to launch in September.

Michael Liefeld, Bureau of Development Services enforcement program manager, says the city would investigate illegal residential parking rentals only if someone complained. Catching someone doing so would be difficult, he says—not like, say, a neighbor complaining about a fence that's been built too high.

“The fence isn’t going anywhere,” Liefeld  says. “If we’re trying to verify if a vehicle that is parked is a violation—that’s a little more tricky.”

Ashman says he researched city code but struggled to find any reason his startup would be in violation.

"The only thing I think is going to happen is, the city is going to send me big letters in the mailing saying you can't do this because of some weird ordinance," Ashman says. "Depending on how popular it gets, [the city is] not going to sit still. They're going to want something. It'll be a fun ride.”