A good tablet should last you five years or more. You are looking for something with a high-resolution screen and a pen that feels natural, not laggy. If you buy a cheap one now, you will just end up replacing it in a year when your skills outgrow the hardware.
New models usually drop in the spring, which makes the November sales the perfect time to grab last year's flagship. The tech does not move that fast, so a year-old pro model is almost always a better deal than a brand-new entry-level one.
This is not a gift from the bank. If you still have a balance after those 15 months, the standard interest rate kicks in on whatever is left, and that gets expensive fast.