Haw. Rev. Stat. § 486N-8.5: Payment of contract price.

Every health club contract in excess of one year in duration shall provide that the contract price be paid by an installment plan, whereby no more than twenty per cent of the contract price can be paid as the initial payment, and the balance of the contract price shall be paid in equal monthly amounts over the remaining term of the contract. The health club shall be entitled to charge interest on the overdue unpaid balance of any monthly installment subsequent to the initial payment. The interest charged on the contract shall comply with chapter 478.