What can be done if I have a tenant who changed the unit's locks without permission from the owner?

First, try talking to the tenant. Explain why you need a key and perhaps he will just agree to give you one. If that doesn't work, then we come to the question of whether the premises are still on a lease or whether it has turned into a month to month tenancy. If the original lease term (and any extensions) has run out and the tenant merely stayed on, paying the rent month after month, then he is considered to be a hold over tenant and you may change the lease terms with a 30 day written notice. In this case, the new lease term would state that the landlord must be provided a key for any and all locks on the premises. After proper service of this Notice, the new rule would go into effect 30 days later. However, if the lease has been continuously renewed and is therefore still in force, then you might have to wait until the end of the current lease term to change or add any new provisions. You should let the tenant know, however, that you still have the right to enter in the event of any emergency, whether or not he is home and if you don't have a key, you might be required to break the existing lock. Your situation illustrates why it's always a good idea to have a lease reviewed by an experienced attorney who could point out clauses that are missing and ought to be included. A smart layperson might read a lease and think that the terms that are there are acceptable, but it's unlikely that he will be able to note the MISSING points that should be covered.

If they changed the locks at their cost they need to provide you a key.

Is it a month to month tenancy, so that you can propose a new contract for the next renewal date? Point out to her that you can only come to make repairs after giving at least 24 hours notice for a mutually convenient time or in case of emergency. Tell her why you want access.If there has been no inspection for several years, you need to try to make one. I know some tenant attorneys argue you have no legal right to a key. However, the tenant should have gotten your agreement to make a physical change in the unit.