ok so you are trying to find the cheapest way to get into this campground you already selected.
You can easily not deal with propane in a way on heating cause you can 'go electric' and buy a heater to plug in. But your campground electric charges could be very high etc. depending on how that cg handles that charge in its rates.
you might hate propane but your cg might have the propane truck come around like once a month or more and ya get on the list for fill ups so you do not have to haul your tanks anywhere for fill up.
So I guess it is all about your selected cg and how it works. What perks are available, being offered by them.
a park model can be as basic as a regular old rv but the park model will be more unmoveable for good towing etc....so ANY camper will suit you in a way. Park models can be hooked up into septic etc easily and if ya throw money at one you can do the skies the limit kinda set up.
You are doing a cg site with hookups.
ANY camper that suits your needs is fine.
then find out if propane truck comes to the cg and fill ya up easily.
get elec. heaters as needed and double check how elec. is charged in this cg.
Any life living isn't cheap in a way :) but I am sure you can make this fit your budget somehow.
Water heater if just you on proane is kinda like nothing. A regular old quicker shower isn't going to use up a tank fast. Regular old cooking won't use up a tank fast really.
So hope some of that helps you in a way :) I wish you the best in finding what will suit you cause when rushed, it is never easy to find the best solution when under the gun to get'er done!