I was not aware on point 4 regarding collecting rents.

Like @Miguel Del Mazo I collect LTR data from BP rent calculator and multiply by 1.5x. 

Here in Philadelphia the water bills are split into two line items, usage and storm water collection.

Hosts are required to collect this tax from guests and remit it to the city or county monthly or quarterly.California State Income Tax: Income earned from renting out a property must be reported on your state tax return.

I collected rent (with increases ) for those 4 years .

Then comes collections.

Assuming you do not get whacko judge, the unpermitted unit has no impact on collecting rent or the eviction process.  

We know there need, want and interest, we have collected all the info, they have been well informed and educated of the process, it's now all but a functionary call, to complete process items. 

They have a mental list of hard to collect rent addresses and they may help connect you and the owner. 

This is an exception under all insurance policies so the next question is even if successful with a claim how confident are you to ever collect from this seller without insurance cooperation?