Water meter question

[Majid Tahir]

Good afternoon everyone, 

I have a question regarding water metering.  I'm in the diligence period on a duplex and it looks like the previous owner payed for the water despite there being two meters.  Looking at water bill, it looked like one meter was disconnected and the other was used to for both units.  Here was the message from the seller:

There are two bills each month because there are two meters. One is disconnected so the charge is always around $39. The disconnection happened before I bought the property so I have no detail around it. The new owner may consider reconnecting it so the tenants pay their own water. I never got around to doing that. The other thing they could do is request that the meter be removed or taken out of service in order to drop the $39 charge.

My questions are:

1. 1. How can one meter be used for 2 units?
2. 2. Since it already has 2 meters, it seems like it would be easy enough to make the tenant pay for water by reconnecting both meters.  How much would cost me?  Is this as simple as talking to the city to enable it?  Would contractors be necessary?
3. 3.  Anything else I'm missing?

Thank you for your help.