@jb-gbaeza Before buying the cell phone, check the devices IMEI online (for free) to see if it has been blacklisted, which means the device is stolen, been lost or been involved in other criminal activity.
The IMEI can be found on devices System settings, on the SIM Card tray sometimes (usually require a magnifying glass) or on a label on the back.
If your device is stolen from you, simply having a pin lock/passcode is good enough to stop the casual thief accessing your data, but if running a custom ROM or UT and the bootloader is unlocked (a requirement to install UT) the device can be reset and used again, unless you report it stolen and get the IMEI blacklisted.