Owning a car for outdoor gear is mostly about managing the hidden costs. You already pay for gas, insurance, and maintenance, but the real price is the utility you lose when your gear does not fit inside. Early spring is when retailers start clearing out last year's inventory to make room for summer stock, so that is usually when you will find the softest prices on mounting hardware.
Negotiating the price of a vehicle is a separate game from paying for the extras. When you are adding a custom rack for a kayak and a bike, using a specific card window for the purchase allows you to keep your cash for gas and park fees. It turns a big $800 hit into a manageable monthly line item while you get out on the water.
The 0% rate is a deadline, not a permanent feature. If you still have a balance on the card after the 18 months are up, the standard variable APR will apply to whatever is left, which makes your gear much more expensive.