Keyless locks to avoid rekey costs

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Hi, I am thinking of installing these electronic keyless locks to avoid rekeying fees for new tenants. The lock I have chosen is this: http://www.lowes.com/pd/Schlage-Camelot-Satin-Nick...

Question: This lock has a keyhole and comes with a key (for emergency unlock purposes). If I don't give the tenants the key, can I just change the electronic combination everytime a new tenant moves in? Just want to be sure this is legal and I'm not violating any tenancy laws.

Thanks.