Changing a lock is simple. Replace the current locks with new locks yourself by unscrewing the old lockset and setting the new lockset and secure the screws. Keep the old lockset and interchange doorknob sets and deadbolts between tenancies.
Electronic locks and keyless entry are another option. The tenant is not provided a key and the access code can be changed by the dominant access code (which is the LL's). The LL should keep the key for security.