They can be! Big name retailers like Amazon, Walmart, and Best Buy offer refurbished, pre-owned phones that have been inspected for damage and tested to ensure they work properly. They also often have limited warranty coverage for pre-owned phones to give you peace of mind as well as tech and repair support if you need it.
You can also search second-hand seller sites and apps like Craigslist, Facebook Marketplace, and OfferUp to see if you can get a new-to-you phone on the cheap. But you should take measures to protect yourself from scammers, including: asking for video proof of the phone booting up to a home screen, video proof that the phone has been wiped of any previous owner’s data, and photographic proof of any model and serial numbers. With this information, you can double-check a seller’s listing against official product specs to make sure you’re getting what they say you are.
And when meeting sellers to pick up products and give payment, make sure you let trusted people know where you are, what you’re doing, and when you expect to return. That way if something goes wrong, they can alert authorities for help. It’s also a good idea to bring a friend with you to seller meet-ups, since scammers are much less likely to try anything untoward if you aren’t alone.