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.

And we ask him if he wouldn't mind reporting to us in 12 months on the amount of savings he experiences from switching from incandescent bulbs to CFLs.

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.  

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%.

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.

Replace all the incandescent bulbs with CLFs or LEDs, including common areas.

I'd say the most used common hallway lighting solution is a 60 watt incandescent(or the swirly fluorescents.)