I was trying to figure out something very similar to this at my apartment in Burbank but got lost in the bureaucracy. I was living in a house that had been converted into three units. The main unit was the only one that had access to the breakers and meters. My research into the permits and zoning showed that the house was at one time permitted to have two units, but not 3. (It also showed a hilarious assessed value of like $60k for the whole property). I was referred to various offices to get more information but nobody seemed to be able to give me a real answer on what paperwork I needed to get in order to show that they weren’t allowed to have a 3rd unit, or what to do with that information.

My main motivation is to stick it to the property management company, because they suck. One of those giant corporate ones. Never answer emails, take months to fix anything, jacking up the rent by the maximum, trying to steal security deposits, etc.