Also, if the unit dies, you will lose heat and hot water both at the same time and have to repair/replace the entire system.I would stick to a traditional boiler and water heater unless space were a factor to consider. 

This is what one company's tune up entails:Spring AC tune up:Indoor Unit*Blower Motor *Amp Draw *Bearings *Blower Wheel Balanced *Control Board *Operating Properly *Incoming Voltage*Connections *Low Voltage *Electrical Connections *Change/Clean Filter *Capacitor *Thermostat *Check Operations *Outdoor Unit*Compressor*Amp Draw*Condenser Fan Motor*Amp Draw*Bearings*Capacitor*Electrical Connections*Clean Condenser Coil(water)*Check Refrigerant Levels*Check Contactor *Relays Operation*Check Operations*Clear Condensation Lines*Furnace:Fall Maintenance Checklist*Replace Filter*Electrical Connections*Check Thermostat*Verify Blower Condition*Check Control Operations*Check Control Board*Check Capacitor(s)*Amps of motor operations* Check Relays*Heat Exchanger Condition*Burner Condition* Remove and clean flame sensor* Inspect Blower Wheel*Inspect and check ignition operations* Check ALL safety operations* Verify a good clean burning flame*Are these pretty standard work supposed to happen for tune ups? 

I currently have a 3 family and plan to spend some of it fixing up heating system, painting, and remodeling 3 bathrooms. 

Taxes 45-50k/year with the potential of going up significantly (shouldn't exceed 6% in a single year)Heating PBO = ~$2500/yearwater PBO = ~$1000/yearelectricity for common areas = $500/yearAsking price $800kHere are my calculations, assuming 25% down payment, 800k purchase price, no estimated repairs (although this is wrong, since i'm sure I will have to fix a number of things for the building with no c/o), but I have excluded that building from the income calculations except for scenario B, where I assume i'm able to add $150 rent/unit and a modest 2k rent for the 2nd building.I've also been informed that this will not qualify for conventional loans because it's a mixed use + over 4 properties.

Then I look at other things like heating, electricity, and if the house is insulated/gaps can be fixed.

I am thinking about purchasing a two unit where one side is oil heat and the other is natural gas.

Needs a kitchen, 3 of the 4.5 baths, new central heat/air and removal of wallpaper and lots of painting.

We will know more in the spring when the markets heat up.

The thing that drags it down is the oil expenses for heating it.

An issue that I am currently working on right now is keeping track of the heat in my vacant rentals (25+ units at any given time).