Technically, unless you buy it from an authorized Apple retailer, it is used. Even if you buy it from a store, if that store is not authorized by Apple, they are selling used devices because they are only new when bought from an Apple authorized store or Apple itself.
My concern would be that the phones could even be stolen, in which case you may quickly encounter activation lock. Apple has two related features, Activation Lock ( Activation Lock for iPhone, iPad, and iPod touch - Apple Support ) and Find My ( iCloud+ - Find My - Apple ), which are designed to prevent anyone else from using an iPhone, iPad, or iPod touch if it's ever lost or stolen. Deactivation of either requires knowing the Apple ID and password that set the feature, or by placing a special request to Apple to reset the device. This Apple ID information essentially defines the current ownership of the device.
If you do not know the required information, are not the signed-in owner, or do not have Apple accepted proof of purchase, get the owner of the account to remove the lock (the section: "If you no longer have your iPhone or iPad" in: What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support ), or return the device for a refund, or recycle the device. The device is otherwise useless to you. If the owner is unknown and has not provided contact information as a message showing in the login screen, there is no way to contact the owner unless the person who gave you the device knows them.
