You are buying this desk so your back stops aching and you can finally stop hunching over the kitchen counter. Get a dual-motor frame with a sturdy top, and you should only have to buy this once.
Shop in January when office suppliers slash prices for home-workspace resolutions. Look at last year's desk models right after the new versions drop, because you get the exact same heavy-duty legs and motor for a lot less cash.
That zero-interest window is a hard deadline, not free money. If you still have a balance left when those 18 months run out, the regular interest rate kicks in on what you owe.