You don't need security cameras to monitor them.

Steel doors and frames; Gated perimeter and main entry access with high security keys that cannot be copied (not just stamped "do not copy") or an access control system that uses rfid proximity readers, with remote access; excellent dusk to dawn lighting with poly-carbonate and/or protective screens outside; timed led interior lighting common areas; a quality, well featured and easy to use remote access security camera system; card operated laundry equipment in well lighted, space with folding tables and vending machine(s); establish "House Rules" for all with a stepped schedule for fines, use the camera system and access system to identify violators (including those dumping trash in the alley) and assess fines (or report to PD) promptly and consistently; do not hesitate to get rid of any troublesome tenants...DO hesitate to accept questionable prospects.

I would appreciate any recommendations from those of you who use cameras for security purposes. 

@Steve Sorensen Over the years, I've used both the Nest Cameras (by Google), and the Wyze cameras.

Also install cameras you can view on the exterior doors.

I'd spin it that you are doing this for her so that noise is minimized.Might want another camera facing toward her house so you can document anything she is doing.

Before you do anything, I would put up security cameras.

Adding Smart home Network to buildings so Security cameras and Sensors can report back via our new smart phone app.

I am currently Wholesaling properties in Southern California to help investors find distressed properties they can cashflow.When I am not doing real estate, I am producing, directing, or have a camera in my hand filming documentaries with my company of 15+ years Documenting Life Productions.

We had a camera run down the line to see if we had a partial collapse in the line.