@Sooyeon Kim you want to get a home owners policy that has coverage for tenants.Also,If you will be living there, you would want some Personal Property coverage. 

They can possibly get water back up on their own policy as well, but this would just be for the personal property rather than fixing damage to the home.Personal Property coverage is normally 70% of dwelling if you feel like this is overkill, potentially you can ask for an override to lower the coverage.

I wonder if there are any insurance companies that offer oil tank policies?

I also wanted to change the lock for the remaining 2 tenants's safety but they don't want to pay for the new keys stating the one who left need to be accountable for his actions.  

If these folks haven't been seen smoking on the premises (which is a stretch of a policy, in my opinion, to include the exterior), why jump to the conclusion that they do so inside as well?

I'll bet it's a major consideration for families (behind safety and school district).

The 3115 is "Application for Change in Accounting Method" and the accounting method he would be changing is to go from a policy of not deducting depreciation to a policy of deducting it.  

I get it that there should be basic protections of health and safety and liveable standards. 

I admit that being in my neck of the woods sometimes makes me scratch my head at some of the West Coast policies.

If she doesn't remove the dog then file for "cause" failure to control her animal, you have the reports.Honestly your rental business is in my opinion in a kind of jeopardy, if this dog attacks another person on your property and you have not taken steps to remove it or notified tenant to have it removed I would guess who is the injured going to also sue.. guess who...you... at a minimum the tenants should have a insurance policy on their dog and you should have record of that along with vaccinations.Security deposit is refunded within the guidelines your state requires, once tenant is gone.