Is there a California law stating that if tenant lives on property for certain years the property is theirs?

No. I think you are referring to adverse possession. In adverse possession, you have to have full open and hostile use and pay the property taxes on the property for a number of years. Simply being a tenant does not confer any property rights outside of the lease.

no

Not only no, but hell no. What planet are you from? Can I buy some of your drugs from you?

No such law exists. -Unless- It clearly states in your contract that you are in a rent-to-own property and you have paid the entire owed amount in full, doesn't matter how long you have lived there

Think about that for a minute - if there were and someone rented long term, they'd then own the property? That would be pretty crazy even for California!

Good God, no! Where did you hear this one?

You're thinking of squater laws..which were used back in the days when property was either abandoned or was state, or fed property.
The laws were changed and now it's considered trespassing if you don not have permission to live there.

Research California Code of Civil Procedure 321 through 325, Google search will get you started. Also, there will be Title Insurance Consequences if IRS back taxes or child support liens are filed against the property.

No, of course not.

That is the funniest thing I have heard in awhile!

No, you are not under any risk of a renter stealing your property because you rented it to them!

There is no such "law" anywhere. Don't worry.