Flying an RC Plane or worse a helicopter is very, very hard, and very expensive to learn as you will probably crash a few.
Second, you do not get live video. So if you can master the flying, you send the drone out, record video, get it back, download it to your computer, and find out the height you were at, or resolution was so poor you have no evidence anyway (assuming this if for people encroaching on the property). if it is for just examining inaccessable areas it will be cheaper to have a friend go up and shoot from their plane. Remember that most private pilots cannot be hired, so offer them gas money as reimbursement.
I am speaking from a low price point. You can get live feedback but anything of quality and distance is very expensive (100K plus investment)
here is the cheapest live video one I know of, but I think the images would be terrible as there is no zoom and the camera is low grade
Draganflyer X4-P Four Rotor UAV Helicopter Aerial Video Platform
We use remote helicopters all the time in my business, and now news crews are starting to buy into them.
Drone policing in the US is, well, inevitable I know of a case that is being tried where the guy said he was being spied on by a drone and wants his conviction overturned. In LA we see helicopters being used in detective work. They fly slowly above a moving car... tracking the movement from a distance (Of course there is the police chase stuff but I am referring to more covert actions).
A vendor and reel
Flying-Cam // Close Range Aerial Filming
And a fun demo
Watch Ninjas Flip Out And Kill While Filmed by RED Epic Drone Copter