The big problem with used, you probably get cut wires and no instructions.

The no instructions may not be a big deal, but then again there may be features you would never figure out.

I just saw one if you hold the lever on the controller, turn the engine off, when you release the lever the trailer brakes stay locked.

Very handy for loading machinery on a steep hill.

Don't remember the name, but it came from Tractor Supply and was slightly under 100 dollars.