What's the best way to sub meter a multifamily?

[Brandt Tingen]

I have two duplexes I want to sub meter.  Meter is very accessible in front of the house in a via a man hole cover, plenty of room to install additional equipment.  The large sub metering companies don't want to mess with it because it's not enough units.  A lot of plumbers aren't familiar with it.  If I research which sub meter I want is any master plumber capable of installing?  Or should I find someone with experience.  I looked into it and it looks like in my jurisdiction sub metering is legal.