If you want to buy and sell or, part out cars sell parts in Hawaii you will need a license from the city and county. There is one tiny little office with no windows that takes care of the licensing for the City and County. This office only accepts mail in applications. To get this application you must send a letter to:
City and County of Honolulu
Department of Customer Services
Division of Motor Vehicle, Licensing and Permits
P.O. Box 30310, honolulu, Hawaii 96820-0310
They will send you back a packet that has some simple instructions, some tips, and a letter to remit your payment of 10 dollars. The $10 dollar fee is yearly. The important points on the letter are that you need to keep track of the Vin of the vehicle and what parts you sold associated with that vin and how much you sold those parts for.