New construction is already installing at a minimum 93% efficient furnaces, seer 13 air conditioners, R-49 insulation on the roofs, R-20 in the walls...

Example: An air conditioner goes on the blink and it takes the property management company 3 to 5 days to get price quotes and then has to make several communications with the property owner to get an approval.

So water heaters, air conditioners and similar items are in scope. 

There is also the reality that furnaces go out in the dead of winter and air conditioners go out in the dead of summer.

There is some rehab involved as far as the roof, old air conditioners, a few water heaters.

Just buy an air conditioner. 

So, we had an electrician come over and to our surprise, due to a dedicated circuit that was installed for the air conditioner unit (needs repaired, but circuit is fine), the process of wiring/installing electric baseboard heaters is fairly cheap and easy to do.Having said that, I am racking my brain for possible pros and cons of adding these heat sources and being able to call these "bedrooms".

If a B+ neighborhood in NYC is at risk of someone stealing an air conditioner, a B+ neighborhood in NYC is a risky place to invest. 

There's not much ventilation so I thought about adding vent fans or windows to the hallways and stairwells as they all have at least 1 exterior wall.A cheaper and easier solution I thought might be a commercial grade air purifier in each hallway and some plug in air fresheners.Every room has 2 vent fans, a window, and a through the wall air conditioner so the rooms have good ventilation but the hallways can get stagnant, especially in the summer when it is hot(no a/c in the hallways and stairwells).Any suggestions that don't cost a fortune? 

There's not much ventilation so I thought about adding vent fans or windows to the hallways and stairwells as they all have at least 1 exterior wall.A cheaper and easier solution I thought might be a commercial grade air purifier in each hallway and some plug in air fresheners.Every room has 2 vent fans, a window, and a through the wall air conditioner so the rooms have good ventilation but the hallways can get stagnant, especially in the summer when it is hot(no a/c in the hallways and stairwells).Any suggestions that don't cost a fortune?