A number of the new trailers are wired for the Furrion FOS48TAPK-BL. It can be had for under $300. This is an observation and backup camera.
The main way an observation and backup camera differs from a backup cam is that it has faster response time necessary to video moving objects. In other words cars and trucks encroaching from the rear. Backup cams cannot process video that quickly.
The Furrion comes with everything necessary to mount it on an unprepared RV, except for sealant.
If you have a newer RV, the manufacturer just plugs the hole where the camera will be mounted. You unscrew 4 screws and remove the blank plate, fish out the power connections, plug in the new camera, fuss a little bit getting the cables out of the way, install 4 screws mounting the camera, power on the receiver, then set orientation (left/right/up/down) and then you are done.
Most of the trailers come with the camera power connections full time hot. The camera draws about 300mA. Not a lot of power, but if the RV is not hooked up to shore power, it will eventually discharge a battery. Some RVers have installed a switch so they can turn off the power to the camera when they are long term storing the RV.
I have installed but not taken the camera out on the highway. At least in the driveway it seems to work well. The range is far beyond 100' spec for the camera.