Any expenses you put in to renovation or repairs are not deductible, but must be capitalized after the property is in service. 

You operate a trade/business - then you have all deductions AND an obligation to issue 1099sB.

An expense is relax deductible.

Can we as landlords stick together and deduct all the non pay rents from our property tax?

They analyze components such as cash flow, principal paydown, appreciation (both home and renovation), initial equity, depreciation, and interest deductions for tax savings, giving you a clear picture of individual gains and ROI over 30 years.

I was told I can pay $3k to remove the part of the tree that's hanging over the garage (in addition to the $3k deductible I'm already paying) or I can take the next door neighbor to civil court because the tree over the garage is actually dangerous to the tenant who lives there. 

Also, not all labor is immediately deductible.

Aside from filing a police report, your insurance should cover your damages less the deductible, and will abrogate damages against their renter's insurance if they have it. 

Our portion out-of-pocket was the $3K deductible. 

@Saika Maeda Permitting the ADU allows you to claim depreciation, operating expenses, and other tax deductions, potentially reducing your taxable rental income.