Have only needed to replace a navien water heater and fix a toilet.

What I all the back end of real estate IE title insurance functions are so foreign to 99% of investors they have no clue on how any of this works if there is a water landing. jsut because you have title insurance does not always dictate a fast pay out or a payout at all..

So long as the water doesn't come from Back Bay. . .

There are water leak detection alarms you can install in the basement--probably some that will alert on your phone. 

The house was built in 1930s so pretty old but has no water leaks or anything like that in the basement.

Not to mention 5 daily showers running up the water bill, the 5 cars they drive and make parking impossible for neighbors.

Open every cabinet door, test all appliances, run the water—both hot and cold.

Buy in major metropolitan cities of 50+ units with city sewer and water.

There is one vacant lot, a whopping 218 square feet (you read that right) in the middle of nowhere surrounded by water district land that last sold at a tax auction 9 years ago for $25K.  

Since each side will have it's own water meter and electric meter, we will need a permit for each side.