You want a system that lasts, not a pile of plastic that wears out your records. Investing in a decent turntable and speakers now keeps you from needing to upgrade your entire setup after only a few months of listening.
Wait for Record Store Day sales to find hardware deals. If you aren't chasing the newest release, look for last year's floor models or open-box gear, which often function just as well for a fraction of the price.
Remember that 0% interest is not free money, it is just a deadline. If you have a balance left when the 18 months are up, the bank will start charging interest on whatever remains.