Can you guys help me I like to turn my property into a halfway house for ex convicts to rehabilitate as they transition into the workplace.

Is tankless electric water heater efficient enough to heat up the water for shower/dishwasher/laundry. 

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.

What would be the best and most efficient way to utilize these funds to acquire the most amount of rental properties and cash flow possible.

However, you've come to the right place to ask opinions on what would be most efficient given the few things we know about you. 

It also creates efficiencies, compared to a collection of smaller investments.  

Then my pro forma with market lot rent & efficiencies has it back at about $2K/mo cash flow.I'd have it paid off in under 17 years and cash flow in the mean time.               

In a smaller multi-family that is already fairly efficient it might be difficult to move the needle.

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.

It really depends on the layout of the building, etc.If the plumbing isn't an issue, I definitely recommend the high-efficiency, direct-vent gas boilers.