Examples include (USB outlets, updated digital thermostat, updated light fixtures/faucets,etc)Any ideas?

I pay for gas heat at one of my 4-unit properties, and I can live with that because I can control the thermostat, but ceding control of electric would be a red flag for me.

My thought on the water heater is that it either has a leak or broken thermostat making it run continuously.

When my preferred vendor went over he found that the "HVAC TECH TENANT" installed a Programable thermostat (not recommended in Rentals because some tenants don't know how to use them), and shorted the 24v circuit to ground thermostat circuit to ground.  

There are two solutions that we topically recommend: (we are a license HVAC company in the DC are) one is to separate de ducts for each floor, and add automatic dampers controlled by thermostats on each floor.

At this point I was getting tired of racking up a tab to this company and I decided to get a new thermostat to see if that might make a difference.

(You charge less rent because tenant covers utilities.The reality, in my area where we include some, is that you can benefit more by insulating/ control thermostats and implement water conservation, because the market rent is set at a higher nonconserving threshhold.

Wi-Fi thermostat to keep electric bill down but also ensure guest check into a comfortable room.

For this I'll assume worst case:ARV - $190K(No closing costs for buying- cash deal) Purchase - $157KThat leaves $33KFloor repairs - $5KHVAC repairs (if needed, its old but I don't know if it works) - $4KVarious replacements (window seal, replace thermostat, one or two panels of vinyl siding) - $2KRemaining $22KSales Agent Fee (6% at $190K) $11,400CLosing costs selling - $5KProfit remaining: $5,600I have a friend that has flipped a few homes and he says there doesn't appear to be any unforseeable problems - it seems like we should be able to paint, clean up and do the rest within one month. 

Wall heaters and thermostats for each unit.