What to watch out for? Rural rental, N. CA.

[Bob Beach]

My 94-year-old dad has a rental outside of Sacramento. Small town, in the country, 2/1 on one acre.  My sister and I have delt with it but different opinions on how to manage it so it's now 95% my sister.  The tenant has been a problem from the beginning, such as behind in rent for a year, buys a brand-new Jeep, lies about ex-husbands job, child support, court cases, etc...

Now, the house needs a new deck, so I went up to inspect it. I found that the tenant has turned the property into a small farm. multiple pens set up with at least one pig, 4 or 5 goats, more chickens and ducks than you can count. The garage was open about 2 feet and had a screen in front of it so I imagine there's animals in there too.  In addition, there is an above ground pool, maybe 3 to 4' deep. The tenant never asked permission for any of this. I have rentals in TN and one tenant put up a pool and our insurance cancelled us till we had the PM get them to take it down.  We also have a "no pet" policy were a couple tenants brought in pets that caused issues. 

My sister did not want to get rid of the tenant because she was afraid, we would get "a bad person in". I've talked to my dad multiple times about the pool and animals, but he doesn't seem too concerned. My sister doesn't think anything I say is true. What are the liabilities? Thanks for any information.