Garage Conversion to ADU -Tenant in Main House

[Jason Pan]

Hi I currently have a SFH rental property in Los Angeles CA, Im also considering turning the Garage into an ADU rental for extra income.

How do I let the tenant in the house know, are there any legal issues I should be aware of?  Should I wait until they leave (dont know when they will move out) or offer them reduced rent for a few months etc due to the noise of construction and now having to share the area with another renter, am I even allowed to do this?