Update:
I skirt the RV in with r6 foam insulation. I put an outdoor thermometer just under the waste dump gates so I can tell when it's freezing. I put a 1200 watt oil heater on top of two cinder blocks, then I wrapped the connection between the extension cord and heater plug with electrical tape so water can't get to it, I snaked the cords off of the ground and onto the underbelly of the RV, and I ran the extension cord through the pull out into the RV so I can turn it on and off with the plug whenever I want.
Not gunna say it's perfect or the best, but it's working out well for me so far. Thanks guys!