We have a heat vent coming out of the cabinet below our sink. 

The past six weeks the heat in my apartment has been erratic, sometimes with the furnace just not working.

For HVAC, I think split type of A/C unit should be fine for both cooling and heating for 700sf space, run by electricity, given the mild CA bay area's weather.   

Here are some of the options we are considering:1) Keep the system basically as is, but update it for greater energy efficiency. - Install two new high efficiency condensing boilers, and update windows and insulation for better heat loss performance.PROS - a) minimally invasive; b) can provide 15-30% reduction in heating costs (we are told).CONS - a)total gas expense is still paid by the landlord; b) individual units won't have individual control (except for a thermostat controlled shutoff valve for heat/water in each unit); c) AC would be available on with in wall/window units. 2) Try to individually meter each units' gas and provide each with a traditional forced air heating/cooling system.PROS: a)gas expense could be completely removed for landlord (huge)- even tankless hot water could be installed in each unit; b) each unit would have their own climate control.CONS: a) constructions costs of running new gas lines and soffiting sheet metal duct work. b) highly invasive with collateral construction costs; c) future costs of maintenance on multiple systems vs a single building-wide system. 3) An electric based heating system- This is tricky in my mind because of the high cost of electric heat.

Come to think of it, I have a rental with an oil tank for heat.

One of the cons here is that current owner pays utilities (water, sewer, trash, heat... waiting on electricity #) which average to about $421/mo.

Multifamily is over heated in many markets right now.

Further, it doesn't have direct heat but, instead, uses a space heater.

After purchase I installed new flooring throughout, repainted the entire home, updated lighting to LED, updated master bathroom, replaced old furnace, air conditioner, and propane with a energy efficient geothermal system that heats, cools, and heats domestic hot water.

I also make an effort to be a resource for their parents if they are in the picture or are paying.Cons:- They're typically clueless on easy fixes such as light bulbs, tripped electrical circuits, and they leave windows open with the heat on.