State and city officials Monday urged people to walk through a 408-square-foot accessory dwelling unit temporarily erected on the grounds of the state Capitol to see whether it could help them generate rental income while easing Oahu’s housing shortage.

Honolulu started waiving up to $10,000 in traditional home construction fees for ADUs in 2015. Since then 150 permits have been issued, and preliminary paperwork has been started on another 1,200 applications, said Eileen Lacaden, community and development specialist with the Hawaii Appleseed Center for Law & Economic Justice.

But more work needs to be done on issues such as parking and sewer capacity to ensure that more Oahu properties can accommodate ADUs, said Council Chairman Ron Menor, who introduced the concept before the City Council in 2015.

For instance, technology such as composting toilets could be explored to see whether they can help deal with sewer and other limitations, Menor said.

It’s estimated that 120,000 lots on Oahu could accommodate a 400- to 800-square-foot ADU, which is supposed to be used as a long-term rental unit and not for vacation rentals.

Mayor Kirk Caldwell maintains ADUs could be a critical way to ease Honolulu’s housing shortage while generating income for local families who rent them out.

“How do we build housing for the people who were born and raised here so they don’t have to leave?” Caldwell asked.

State Sen. Josh Green (D, Naalehu-Kailua-Kona) called ADUs a “game-changer” and pledged solidarity with the city and nonprofit organizations to support ADUs.

Across the islands, Green said, 200,000 people “are just a couple paychecks from dangerous times, not being able to afford a home.”

The unit at the mauka-Ewa end of the Capitol grounds — at the intersection of South Beretania and Richards streets — cost $20,000 in materials and was designed as a “packaged home kit” by Honsador, Lacaden said. It includes 100 square feet of lanai and was equipped with more than $60,000 in furnishings.

Construction began Tuesday. It’ll remain at the Capitol for much of April to allow people a chance to “find out what it’s like to live in one of these,” said Gavin Thornton, co-executive director of the Hawaii Appleseed Center.

Caldwell called Menor “the father of ADU.” But Menor said he got the idea after reading a policy paper on ADUs written by Hawaii Appleseed.

“I’m glad it’s finally becoming a reality,” Menor said.

While House, Senate and Council representatives welcomed more ADUs as a way of adding housing inventory on Oahu, they also pledged their support to get more built.

“We’re going to work with you, united,” said state Rep. John Mizuno (D, Kamehameha Heights-Kalihi Valley).