1) Off island owners are not allowed to manage their own property, they must have an on island manager. The property manager must also reside on the same island as the rental.
2) Owners must pay a GET (General Excise Tax) on all gross income rent. You can apply for a GET number at https://tax.hawaii.gov/
3) Rentals less than 30 days are illegal unless you hold a special permit or structure your rental to abide by the timelines.