Bought house with tenant. Tenant doesn't live there. Help!

[John Mich]

So I bought a house cash and intent to flip it. It's a mess. The seller told me there is a rent paying tenant who has been in place for 22 years.  Seller has no lease on file. He says the tenant owns several properties in town and it's likely they live elsewhere. The house is full of cats and cat poop and is completely uninhabitable (I got a killer deal on it, and I knew what I was getting into.)  Judging from the state of the property, and looking through windows, it doesn't seem that anyone has actually lived there for years. It appears they have continued to pay rent on the property solely to house their disgusting cat breeding program.  The best I can tell is that someone comes and feeds the cats a couple times a week.  

The only contact info the seller had was a phone number. I've called it over a dozen times and left several messages. I've taped notes to the door hoping that the tenant will see them and call me.  No luck so far.  I don't even have the tenants name to put on a 60 day notice, and since they aren't living their, do I even need a 60 day to get them out?  This is in California by the way. 

I'm slightly worried about the cat situation as it's quite inhumane, and I'm not sure what my liabilities are as the owner.  Anyway, any help in how to proceed with an eviction would be much appreciated.  

Thanks in advance!