I even spell it out that if there was an LED bulb when you moved in, there better be one when you move out and if there is suddenly an incandescent bulb, I'm charging you for the replacement. 

Toss all incandescent, fluorescent, halogen, mercury vapor, etc.

(I will need to increase that amount as soon as I run out of incandescents that I stocked up on).

For example, if you're using incandescent and/or halogen bulbs(most people do,) while in operation, ten 75 to 100 watt bulbs function as a small space heater would.

All she had were old incandescent lightbulbs which she said they were new.

As a side benefit, whoever pays for water heating will also save money there as less water will need to be heated.Hey, while you're at it- make sure you have LEDs instead of incandescent or compact fluorescent bulbs in the common areas.

I calculated that by replacing the incandescent bulbs with LED bulbs, I can reduce the expenses by $50/year.  

I already have eave mount motion sensing dawn to dusk security lights at each corner but she still feel better with the light directly over the doors.She pays for her own electric so I am not paying for the usage.I read that leaving lights on forever can be a fire hazard but I don't know if that's a myth, or not.The lights are enclosed, ceiling mount lights with a 60W incandescent bulb.

You'll undoubtedly lose a tenant(or three,) but after a year or two you should have all of the units at market rent.Another thing you could do is replace all of the bulbs with LED bulbs- if they are currently incandescent, you can cut overall electric usage by 10-15%.