I would not buy a used phone because an aged battery has a limited life and is expensive to replace. Also, phones have limited support. Many phones only have 2-3 years of updates/support. Once you lose support, your phone may have security vulnerabilities or new apps may not work.
You can sometimes buy a "bnib" (brand new in the box) phone on a discount off of craigslist or kijiji. These are usually "free" phones that people get when they renew an expensive plan, but have no use for the phone.
You can also buy refurbished phones from the big telecoms or from the manufacturer. Often these are new phones that get returned after a plan is cancelled in the first 30 days. Or the used phone is traded in, and new battery is installed if necessary.
Personally, I have been buying the previous year's pixel model when the new model comes out. For example, the google pixel 9 pro is now selling for about $1,400. A brand new Pixel 7a or 8a at the google store sells for about $599 or $679. I have a 7a and it is excellent. Google spells out their minimum length of support clearly and often exceeds the length of support. For the pixel 7a, the length of support is at least up to May, 2028. With Black Friday and Christmas around the corner, there are usually good sales.
