I'm not aware of any payment plans other than the RCI Credit Card. You might get an introductory rate of 0% for a limited time but I don't think they routinely offer 0% interest on cruises. This card does allow you to accumulate points (like frequent flyer) and apply them to future travel. Any cruises you pay for with the card get you double points. Some travel agents will accept partial payments, that way you could pay a portion each month between making your deposit and final payment being due.