I live in Los Angeles and, as most homeowners working in rent-controlled areas can relate to, having renters in a unit paying excessively low rent can be a pain.

You can't deduct any expenses in excess of income. 

Without going into excess detail,  I believe only one of them would have a valid adverse possession claim, based on the dates the houses and fences went in.The crazy thing is that even Google maps clearly shows the conflict between the lot lines and their fences and sheds.

I had a tenant that was finally evicted, that currently owes me in excess of $40,000.

@Jason Sinclair Seems excessive but also not certain what brand the windows you are looking at, the warranty, construction, tempered / non tempered, double hung vs single hung....  

Umbrella is sometimes used interchangeability with excess liability insurance.

How can I analyze if that will allow me to charge in excess of that amount to the tenants (ex. $+200/ mo rent).

Seniors on fixed income with no other income than Social Security DO NOT qualify for food stamps (excess income, if you can believe it!)

If getting properties free and clear is the goal, use the excess cashflow to paydown principal if you want - this is the most "safe" option as it will allow you to add more payments and also give you breathing room if you have unforeseen events (personal or in the portfolio).  

  $90 per unit is extremely excessive and would nearly be the cost of your PM.