Below Ground "Basements" are rare at O'ahu Hawaii due to "the Water Table" being close to the surface, especially near any of the towns, City and County of Honolulu (Entire Island of O'ahu). Because of this building a Home with a Septic Tank is Illegal, as the Sewage from the Septic Tank gets into the underground water wells. There is also the problem of flooding during Winter rain storms.
As of May 03, 2019, Air BnB, and Vacation Rentals are not "Illegal" as have existed before Hawaii had any Hotels. Hawaii Democrats Legislature have been demonizing Vacation Rentals and Air BnB because of the Mainland Hotel Corporations bribes (Campaign Contributions) as Vacation Rentals like Mayor Kim and many at Vacation Land Puna "the Big Island" aka Hawaii Island, and at O'ahu directly cut into Mainland Hotel Corporation Profits of charging over $200.00 a night. see Hawaii Newspaper Star Advertiser.