It pays to check listings, and be sure you know the difference between “seller refurbished” and “manufacturer refurbished.” (There’s a big difference.) Generally speaking, manufacturer refurbished is what you are looking for, especially if you want an “official” warranty. Note that most refurbished warranties even from a manufacturer are usually only 90 days. Some manufacturers offer 180 days, but definitely check the details before buying if that’s something important to you.
I second @rmadaris with the Adorama or B&H suggestion. (Another used dealer I’ve heard good things about, but never actually tried is keh.com) Amazon can be quite flaky, depending on who the seller is. It’s true that “Amazon customer service is excellent”, but ideally you don’t want to have to deal with them, even if they are excellent. 🙂 Adorama and B&H both carefully inspect all their refurbished/used merchandise to make sure it’s described and priced properly. There’s absolutely no guarantee of that from Amazon.