Have you considered LED lighting in your rentals?
I'm very interested in LED lighting, and we're starting to try it in our home. These lightbulbs are (in theory) meant to last 20+ years (ask me when I'm 65 how that's working out.) And they are very cheap to run per year. I'm just wondering if it's a little competitive advantage.
P.S. I saw LED bulbs at ALDI for $6.XX each -- sounds like a good price!