State Specific Question About: CALIFORNIA (CA)

Single detached family home rented to a Hispanic family. We just noticed that the tenant let his extended family members to use the back yard to prep food for street vending. They put two freezers and one fridge outside in the backyard against the exterior wall along with shelfs and racks. They prep food in a table in the yard and use potable stove to cook stuffs. The tenant claimed that this extended family members have permits to do street vending etc. We feel that this is a misuse of space (residential for commercial use), and concern a lot about fire safety because appliances are used outside (with power plugs etc. hanging without protection from water etc.). What should we do?

This is a generally good tenant. The interior of the house is maintained very well. However, his extended family members keep using the house now and then (living with them, vending food prep, etc.).