A good 4K drone isn't a toy. It's a tool for capturing shots you can't get from the ground. If you buy right, you'll be flying this for years instead of replacing a cheap model every season.
Watch the release cycles. New models usually drop in the spring. If you can wait until then, you'll likely find last year's top-tier tech for a better price.
The 18-month window is a deadline, not free money. If you still have a balance when the period ends, you'll start paying interest on what's left.