I wanted to be able to see what traffic was in back of the vehicle behind me so I did something similar on my gooseneck sunrader trailer. I used a wireless system because I didn't want to have any cables between. Used the monitor up front that plugs into the cigarette lighter socket and has an on/off switch in the plug in. Then made a small camera mount that I could mount on one screw of my rear facing camper window on the inside center. I wired the camera to a lighted switch inside the camper door off of house battery. Whenever I'm going on the road, just reach inside the camper and turn the camera on, hit the button for the monitor in the tow vehicle and they link up and I have a rear view camera system! I got a 2 channel monitor so I will be adding a magnet mount batter powered camera for hooking up and backing into spaces. Mine is a DoHonest for $89.95 on Amazon, but there are many.

Please post your pictures 

I finished this project successfully. I used a rear view mirror camera display for the monitor. Also used a 3 ft piece of conduit and welded some 1/2 angle to the end.  Mounted the pole to the bumper. Drilled a hole in the top of the conduit for the camera.  Wires run under the RV and up through the conduit. I can attach pictures if anyone wants to see them.