I own 1 and manage another vacation rental in Haleiwa. I would say North Shore is one of the best areas for VRs. North Shore lacks future development and is becoming increasing popular. However, keep in mind that any VR without a VR permit is a technically illegal operation in the eyes of the state. If you're caught which many operators are on the Windward side & North Shore you will be provided a warning followed by daily fines if continued. Permits are no longer issued and stopped back in 1989.
To start you'll need a lot of capital/high loan Pre-Approval to get into the business. A ideal VR Single Family Homes will start around $1.1M if you want views or are close to the ocean. $700K is the start for a home in a local Haleiwa neighborhood away from the ocean. Condos starting $530K and are nearly non existent in Haleiwa but do come up every year or so. Turtle Bay is closer to Sunset and has Condos starting around $500K. I would avoid Waialua "cement city" for short term rentals since they're a bit farther from Haleiwa Town and any popular surf locations. Those units tend to sit on market for a lot longer than anything closer to Haleiwa
As a owner myself if I would continue to acquire rentals in Haleiwa or Sunset. Being close to all of the restaurants, shops, iconc surf &, snorkel of Haleiwa town, Sharks Cove, and Sunset is very ideal for tourists.