If the other tenant feels it is intrusive, then make the tenant remove it or adjust it until everyone is happy.

We installed an interior French drain system in the basement, because we knew that the neighborhood is prone to water intrusion.

We installed an interior French drain system in the basement, because we knew that the neighborhood is prone to water intrusion.

it should offend him, and so be it.As @joe said this property with a long history of neglect, water intrusion has done far more than bend some rafters.  

Water intrusion may be an issue.    

But both feature modulating compressor speeds so variable cooling which can save on electrical, again more so in the swing months.As you have heard the positive of ductless systems is that the refrigerant lines are smaller than ductwork so they are great for installation in much older building because there is less intrusion of the structure for installation.

AND the feeling of intrusion.

Are there signs of water intrusion on the inside of the structure? 

As lenders we should start using NON INTRUSIVE and LIMITED DOCUMENTATION .

Unfortunately inspectors can’t always catch those unless there are multiple signs pointing to some kind of leak or water intrusion throughout a home.