I think a used one is a great way to start; and then get out and paddle in different types of water so you can get some sense of what you like, what you love, and what you don't. That will provide you with some direction when you're ready to buy a new (or fancier used) kayak.
Most places that rent kayaks will sell their used boats when they upgrade. That is a great place to buy because they generally have baseline/basic very user friendly boats.
Just don't spend too much on a basic used boat because if you get in to it you will want to upgrade within a couple of years.
/my opinion.
