You are buying this to jump into high-end virtual reality with zero compromises on tracking or immersion, so you want a setup that lasts for years instead of leaving you wishing you bought the better version six months from now. A complete kit with base stations and controllers usually runs about $1500, making it a serious piece of entertainment gear that deserves a proper plan.
Keep an eye out for holiday game bundles in December to get extra software value packaged in. If a brand-new generation just dropped, look at last year's model since it often gets discounted while still offering nearly the same performance.
That intro window is a deadline, not free money, so if you still have a balance left when the 18 months are up, standard interest will kick in on whatever is left.