This has been a year long project for me. I bought the meters online, and then asked my best park resident who "knows everyone" if she knew someone to install them, and she knew a plumber who had installed lots of meters. So I ended up paying him about $1,000 to install the 23 meters. Then I found a new yard guy who charges me $40/month to read the meters for me and he emails me the readings. I sent reports to the residents, highlighting each person's usage so they could see how much they were using compared to others. (I have not been billing them for it this year, but immediately the water usage dropped significantly.)
In Florida, we have to drop the rent the value of the water cost, which is a problem if you have to average it based on the usage when it was the most extravagant, of course. Instead, since most of the residents are not water wasters, I decided to include 3,000 gallons a month in the rent, and not raise the rent for 2018, but also not lower it, thinking that the state would find that reasonable if it ever is an issue.
I decided not to hire out the billing because they wanted $2,000 for setup, and a separate bill for water would be punishing the majority of my residents who are not a problem, and anyway, the have no way to enforce payment so how would that help? For the 3 or 4 who will exceed the 3,000 gallons a month, I will send an invoice before the 1st of the month telling them to add the amount to their upcoming rent checks, planning to return their checks until they include it. It won't amount to much (like $3-$7 dollars) so I don't expect anyone to squeal. Yes, it's a bit hands-on for me to have to send out those few invoices, but those high water bills were way more irritating. So we shall see how this goes.