Remember that a broken hot water heater costs about the same to replace no mater what your rent is.

I paid $6500 for a 2 ton with install but it also included disassembling a broken one, haul away and adding a drip pan.

Are you talking about a broken pipe or leaks into a fixture (for example, a toilet always running or a steady drip into the tub)?  

That said, I would upgrade your accountant.

I bought one house at a 7.25 interest rate and the one with all the upgrades is at 3.865.

Unless you do upgrades to depreciate, like another roof, large appliances, AC unit etc.

Also some broken windows.

Inspect for any rot or damage periodically, and replace or repair sections as needed to maintain its condition.Potential Upgrades / Considerations: Security:Enhance security with robust locks, a video doorbell, and exterior lighting.

I'd may send a copy of the rent increase letter by certified mail but maybe not, depending on what all i'd learned so far.I'd always be respectful and positive and stress that the house isn't perfect but my duty is to fix what is broken and their job is to pay on time. 

For example, the PM wanted to charge $300 to replace a broken mailbox.