Ask the seller to follow the steps below to completely erase the device. If the passcode Lock Screen or the Home Screen appears, the device hasn't been erased.If you don't see that screen, follow these steps to check if the device is ready to use:
Don't take ownership of any used iPhone, iPad, or iPod touch if it's protected by Activation Lock. On a device with iOS or iPadOS 15 or later that is protected by Activation Lock, you see an 'iPhone Locked to Owner' screen when you turn on or wake the device. Before you buy an iPhone, iPad, or iPod touch from someone other than Apple or an Apple Authorized Reseller, make sure that the device is erased and no longer linked to the previous owner’s account.