I am in the same situation as you. I own the building and I have 4 rental units, and it is vital to have security cameras not only for safety reasons, it also serves as evidence for bad behaviors or should a crime be committed in the rental units, such as theft. The cameras can prove who entered their unit, show when my housekeeper was in the unit, etc.
My security cameras have caught everything from people smoking in the hallways and common areas, to people using their rentals for nefarious reasons.
And because I have other guests in the building, this keeps other guests safe. In fact, we have had guests comment on how we take security seriously and that provides peace of mind for them.
None of my cameras are inside the actual rental units. They are all very visible, and I have signage around the property that state we have security cameras.
This blanket policy is not well thought out.