Let's talk furnaces! Open to suggestions on how to move forward

[Anthony Simboli]

Hey BP,

I am about 2 weeks away from closing on another property (2 family duplex!). Like my other properties I seem to always find the ones with only 1 furnace. The age of the system is unknown but having some experience replacing them in the past I know it's towards end of life. It is currently a oil forced water burner with 1 oil tank. 

My question to you all is:

1. Should I replace with 1 unit (a stronger and more efficient system) and keep the zones for both units?

2. Should I replace and add a 2nd furnace (2 new systems)

3. (side question) if possible, I'm working with the city right now (Manchester NH) to determine if natural gas is an option and how much that would cost. Has anyone considered the switch and was it worth it?

I'll be living in one unit for about 2-3 years most likely while I rent the 2nd unit. Then the plan currently is to rent both units.

Any information would be great. Furnaces always seem to be my kryptonite so I'm trying to jump on it early before I even move in or rent to tenants.

Thanks!