After multiple go-around with the city(mayor, fire chief, city admin) I am being told I will be responsible for upgrading the city water lines or will need to install a water tank on my property.My contention is that it is their responsibility to have an adequate infrastructure to support the ordinance that they passed.Any references to an attorney would be appreciated

The rehab $ is paid out in installments as work is completed.

Sub metering is installing a meter on each unit.

The rental needed a lot of work, I installed central air/heat replaced the water and gas lines and put new windows in the house.

Friend got it with this at a vacation home.Forget the billing and fix the problem:First take better pictures of the meter and the connection for evidence.Get an electrical contractor to come out, disconnect the illegal connection and install a security box with a lock so there's no access to the power  connects.Write a letter, send it Certified to the neighbor with copies of the tampering that this is criminal fraud and theft and if it occurs again, they will be prosecuted - - clearly note a copy has been sent to the Utility Company.You might research the owner of the property and send a copy to them also (in case it might be rented).You didn't start this but need to control it.

Even if they don't,  also look at your new remodel and ask if you want amateurs moving in appliances that may or may not be functioning (leaks etc) properly or installed properly.

I am currently tearing out my brick fireplace to install french doors, among several other things.

You need a license to advertise a property, no option can give you the right to advertise or show a property and not be considered a listing agreement, such agreements may cause the option to be an installment sale as well. 

Should I install a sprinkler system or let it be? 

However, like an RV a Park Model cannot be permitted as an "Additional Dwelling Unit" (ADU) aka "Granny Flat" and therefore is not allowed to be permitted or permanently installed on a real estate lot or parcel.Unlike their big brother the HUD Manufactured Home, Park Models are built under the ANSI code and cannot exceed 400 square feet of living space.