New Zealand in the winter hits different. The Southern Alps are blanketed in heavy snow, the crowds are gone, and crisp clear days make those massive mountain views pop harder than they do in January. You want to aim for July or August when the ski fields are fully open and the air is biting and clean.
A trip like this usually runs about $5000 once you factor in flights, a car rental, and a few good spots to sleep with a view. Spreading that cost out over time makes it much easier to swallow, but you need a solid plan before you book a single ticket.
That 0% intro period is a hard deadline, not free money, so make sure you can swing the monthly payments before you sign up. If you leave any balance on the card when those 18 months are up, interest kicks in on the remaining amount at the standard rate.