If tenant refuses, you show up with a locksmith and change the locks while the tenant is away, conduct your Lead Paint test, and then start the eviction.I think most of this would be resolved with more stringent background checks and higher standards.Have you spoken to the City about this to see how you would get around it?

I would fix it this time and tell her if it happens again, that she will have to hire a locksmith to replace the door lock at her expense and call it a day.

@Barry RobinholtI have been using landlord locks for 10 years... they are not cheap but I can't tell you how many thousands of dollars we save on locksmith fees.

While they were at the office signing docs, our locksmith was at the property rekeying the locks!

Knowing the location of the home, if it has a basement etc...would be helpful but snaking companies (may be the plumbers, maybe not), HVAC, general handymen/women, locksmith. 

If you don’t know how or can’t get a locksmith out , go buy a new lock set and just swap out .

There is a local property manager that will send a locksmith to make sure we have access.

Many leases incorporate this kind of language or at least state that the tenant bears financial responsibility for a locksmith to change a properly functioning lock.

Locksmith. 

To my non-professional locksmith eyes the blanks all look the same but the copies of my master key aren't turning the lock.