SA Auto Finance Calculator

i want to build a website where people of south Africa who wants to buy a car can do a monthly installment estimate the layout should include 1. Vehicle purchase price 2. Extras Costs 3. interest rate % with a sliding bar to adjust the interest rate up to 20% 4. Term sliding bar in 12 month segments up to 96 months 5. balloon % sliding bar up to 30 % 6 . Deposit , the client should also be able to select any vehicle finance company in south Africa , please take note the contract initiation fe