Generally here's usually a small fee and an annual or biennial inspection for things like fire alarms, peeling paint, broken windows or other unsafe living conditions.

Alarm system?

@Alix Cassagnol converting to multifamily for 25 units you would likely have some ADA and fire department regulations (alarms upgrades, sprinklers) to comply with that an older unit might not meet. 

 - Knob and tube wiring, screw-in fuses, low amperage feed to building - The historical designation prohibits freedom to renovate with modern materials - unlined chimneys - egress does not meet modern code (e.g. window opening size, 2nd egress from bedrooms) - cast iron internal waste or water feed lines - outlets are out of code (GFI for washers, over counters, in washrooms) - hardwired, interconnected fire alarms may now be required - old underground utilities or oil tanks that are not known - dry rot in floors from old water leaks - trees have deep roots that entangle waste lines - nothing, absolutely nothing, is plumb anymore. 

The only detail that's somewhat alarming is the maintenance cost but if you're confident that you can screen for tenants that you're sure won't trash the place then it could go well.

NOTE that a small magnet taped to one of the sensors will stop the sensor from activating the alarm, thus allowing anyone from the INSIDE the ability to exit undeterred.  

Personally, our PM company has seen a slight decline in both showings and applications, however it is nothing too alarming.

If he is a thief then everyone should know it.

Dion, you know those videos of the World's Dumbest Thief, like the guy who stands in line at the bank wearing a mask to rob it, or the guy who locks himself in a freezer to hide or the guy who gets stuck in the hole cut in the roof......you know, those types......How about a thread of the greatest master minds devising note strategies, that can't spell "Promissory Note"? 

She later apologized to us and replaced it.I also got tired of tenants taking batteries out of the smoke alarms and now use only those with 10 year lithium batteries as they can't be removed from the alarms.Gail