On our previous MH we had a back window and we mounted the wireless camera inside the window. It worked perfectly and kept it out of the weather.
We took power from the supply line to the 12v lights in the cupboards overhead the bed and added a switch to turn the camera on & off.
Of course when wet weather covered the window in road grime we couldn't see much but then it would have covered the camera lens if was outside anyway.
'93 HR Navigator 38WB
Towing one or more... 1980 Citroen Acadianne/Jeep Grand Cherokee /1956 Velocette Venom
something for the weekend...1968 Vanguard Camper on 1989 GMC 2500