[source]http://articles.latimes.com/2004/jan/11/realestate/re-aptlife11

Question: Does California law require that a tenant provide a key to his apartment and his phone number to the landlord?

Answer: No. California law does not specifically require tenants to give landlords either a key to the apartment or a phone number, but not doing so may be a bad idea.

For instance, if there is an emergency when the renter is not at home, such as water running out from under the front door from a leak, the landlord will have to break into the apartment to take care of the problem because he has no key. The tenant will be responsible for the repairs to the door and lock.

Also, leases and rental agreements universally prohibit tenants from making alterations to a unit, such as changing the locks, without advance written permission from the owner. When a landlord allows a tenant to put a new lock on a door, he generally requires the tenant to give him a key to the new lock as a condition of the approval.

If you change locks without the landlord's permission and don't give him a new key, or change the lock back to the original one, you may be evicted for altering the premises in violation of the rental agreement. Either way, it's a good idea to give the owner a key.

Similarly, it's always a good idea to give the landlord your phone number in case he needs to get in touch with you about maintenance or repair issues or, more important, in the case of a natural disaster.

I can see my landlord/property manager giving me written permission to change the lock and temporarily not requiring them to have possession of a key. How sufficient or legal is saying something like, "changethelocksLA has permission to change the locks and is responsible for providing a key to [ex-girlfriend] upon request if request is made prior to my own personal possession of the key. I, [landlord], have given him ten days to provide a copy to me. In the event of an emergency need for access (fire, flood, disaster, etc) before my own possession of the key, changethelocksLA agrees to pay for unlocking services."