What I've been considering is installing a few "smart outlets" (outlets with usb plugs as well), a dishwasher, a garbage disposal in the kitchen sink, new LED light bulbs throughout, and some light caulk work. 

What led you down the path of becoming a licensed plumber?

Washer and dryer inclusion may get you an extra $25-$50 a month, but you'd have to check what your competitors are offering as many apartments offer in-home and/or on-site laundry.You can also consider LED lighting, pet rent, storage rental as other ways to add value and increase rental income.

It appears you have found success by achieving a great career to provide for your family but whatever decisions and ways you've chosen to look at life have led you to your current situation.

Not only the equation, but programming that equation into the system so it adjusts the starting temperature according to the current gas and electric rates.)Before doing any of that, I'd make sure the low-hanging fruit has already been picked- LED lighting, water-efficient fixtures(sinks, toilets, shower heads,) possibly spray-foam insulation to reduce drafts, to name a few.MG

It's more than double my last purchase, and that one I got somewhat led by the nose throughout, and it brings some concerns with it.

Also, I’m planning on using LED recessed lights.

That property is now fully rented out, cash flowing more than $2,000 a month and led to the purchase of another building and my partners new home.

@Peter Padalino - couple suggestions, as I've been in your shoes.  1) Go crazy on energy efficient items - all LED bulbs, NEST or EcoBee thermostat, etc, etc.  2) Get someone to quote solar power for the roof if you have APS - I went solar and LOVE IT for rentals. 

One option that I was considering was having a humidity sensor and kill switch, LED lights, etc.