I'm a newbie at real estate investing and am about to purchase an up and down duplex that currently has one HVAC system in place (but does have two electric meters already). Currently, the owner pays all utilities.

Clearly, it's not ideal to only allow one tenant to control the temperature (which is what the current set up is). So, we know that we want to at least add some zoning control so that both tenants have some level of control over the thermostat. But it would, of course, be far better to have everything completely split and provide a separate furnace and hot water heater, etc. for both apartments. 

Has anyone dealt with this? We have no idea what to expect in terms of cost and the HVAC person we contacted cannot give an estimate until he gets into the property, which won't happen until we close. Just want to get a sense of how big of a project this may be. I know it's impossible to accurately estimate because every project/house is different but, again, just hoping for a general sense of what kind of headache/expense this may be.