I had one lady act inappropriately with another agent under me and I quickly resolved it by simply having an email sent to the broker in charge of her area, problem solved immediately.

If it was to build a luxury single family home for future STR usage, SE.

Many of us agents are licensed in multiple states and write business all over the country.

I would recommend A) Consulting a qualified attorney to perhaps draft some sort of Addendum to the lease specificially as it pertains to the pool usage and liability and B) Consulting your home insurance company to see if there is any additional liability coverage in case of an incident with the tenant(s) and the pool.

I would install BTU meters and charge each unit a fraction of their gas usage. 

Definitely convert to phone app usage, as @Jon Crosby recommended.  

Hi Aaron,If you're going to have workmen inside occupied units, might be a good idea to have a member of management/maintenance in the unit at all times with them (to prevent bathroom usage complaints, and to blunt theft claims from the residents) as well as to make sure the interiors are left broom clean when they finish.A paycheck to paycheck guy coming home to find all of his beer gone, or game console missing isn't going to be a happy tenant.Good Luck! 

If its truly being driven by tenant usage then maybe sub-meter, but there is probably something else going on like a leak, faulty meter, or a poorly run municipal water department (my hunch is that its the later).  

We offer free WiFi with an 8 family and saw a steady build-up of WiFi usage. 

That is a very good question, not sure if the law deciphers between current usage or not.