In addition to what others have said, if you plan on using the unit in cold weather, you may want to consider getting a large capacity propane tank rather than fiddling with portable 20lb bottles. The furnace uses a good bit of propane.
Water presumably would need some sort of a well setup, a pump and perhaps an associated pressure tank. You could probably do away with the tank if you just operated the pump to fill the fresh water tank in the trailer periodically and then used the trailer's pump and water system. If you are planning on being there in freezing weather, using the built-in water tank is essential (rather than relying on an external pressure tank and "city water" pressure from it) as the feed hose would otherwise freeze up pretty quickly.
I second the suggestion to size electrical service (and septic and water systems) for more than just the one RV. In particular, it would be a big shame if you ever wanted to build a cabin and had to construct an entirely new septic system and run a new service entrance.