However, due to the whole area now being deemed by insurance companies as a "fire-risk" zone, I can't find a single insurance company to put a STR endorsement on a regular home owner policy up there.

They should put the tenant on notice, and indicate their intent to terminate their lease if they don't correct the problem.If you have no such clause in your lease, you can find the owner of the property using tax records, then skip trace the owner and contact them to let them know of the situation.

Occasionally you can knock on the door and tenant will let you in, or maybe even the owner, but that is probably more rare.   

@Shane Cordrey - Are you looking to primarily invest directly as an owner operator or have you also considered investing as a Passive Limited Partner in Multifamily ?

If you're looking for properties less than 50 units, you'll have a lot of success with calling owners directly. 

That is a failure on the owner's part, for sure.  

Los Angeles make owners responsible for units to be free of vermin.

Also the new owner has the advantage of screening their own tenants and signing leases at or above market rents.

And it is very straightforward to file these, so I would expect it to be well within the scope of any operator sophisticated enough to pull off an owner financed deal. 

At the time of the leak, my tenant was showering, but everything around the bathroom is sealed and in good condition.It’s been a week now, and there have been no further leaks.However, the owner of the apartment below is still asking me to repair their ceiling.