If you are not totaly against paying for software tools that help save your time :) you can try mobile apps like Landlordy, Property Buddy or DIY Landlord (disclaimer - I'm the author of the first one) - they'll help you deal with income and expense tracking with convinience (much better than Excel, in my opinion thanks to integration with camera for receipts and email/messages integration).

No worries about static cameras posted strategically.

We've talked about cameras, an on-boarding process, a check-in/check-out process, among other things - but ultimately we really need to do something differently.  

Motion sensitive exterior lighting and security cameras.

We've had this kind of problem before, and honestly, it seems to just gradually get worse and worse until we can get the tenant out.You can schedule frequent inspections to get inside the house and check the condition and count beds and toothbrushes.You can give your business card to all the neighbors and see if any of them are willing to have a camera to record the house set up temporarily.You can hang back and wait for it to play out.You can stop by the police department and see what they are willing to share and if they have a program where you can copies of all calls to the property.You can send a cease and desist letter stating that if you get any proof of criminal activity or extra occupants there will be no leniency.  

She curses the kids, sprays water on the neighbors, shines lights and camera on their bedroom windows, dumps trash and cigarette butts on their fronts and sites.  

See if you can find plumbers that use the cameras to inspect the lines.  

If you can not replace the cover you purchase a new camera and bill the tenant for the cost of the camera.You may not deduct anything from a tenants deposit that you do not have a actual receipt proving you spent the money.

Also, be aware that any real estate transaction in the city must have a camera and dye test.

Bring a flash light measuring tape camera and goto building Dept and tax assessor.