Every tenant turnover should include a rekey: you cannot know how many copies of the old key exist. Rekeying all exterior doors to a single new key is fast and keeps the existing hardware in place.
Keep a written key log — who received keys, how many, and when they were returned. Consider a master key system across your units so one key serves your whole portfolio while each tenant key opens only their unit.
Smart locks for rentals
Keypad locks remove physical key handoffs entirely: issue a code per tenant and delete it at move-out. HSI Locksmith handles turnover rekeying and keypad installation for landlords across South Florida.