How to seperate electrical on converted 2 family

[John H.]

I have a 2 unit house that used to be a single family.  Right now there is 1 electric meter, all circuits go to each unit respectively it should be simple to add a 2nd meter.  I have never owned a multi before and am not sure how it works.  I will be talking to my electrician next week but I want to gain some knowledge first.

The question is, I need 3 meters, 2 for the units an 1 for owners? Or can I just have 2.

Here's why I think I need a 3rd meter, but I figured I'd ask.

***   There is are 3 exterior doors, so the units do share 1 entry way that has a inside and exterior light.

***   I'm fairly sure I need to install hard wired smokes (building is 100+ yrs old) and since they are shared, i'd have to put these on an owners panel?

***   I need a dehumidifier running in the basement.