Give some thought to folks who don't have a full bath in their camper or trailer or tent (ha!). Many smaller trailers and coaches don't, so if possible, add a bath/shower house - either included in the price per night, or use the pay per use metering system. You'll have to figure out the cost of an 8 minute shower, but I've seen anywhere from included, to $2-$3/8 minutes of hot water.
Another issue you'll have to deal with will be making the facility "accessible" to comply with local regulations. Consider things like wheelchair access, and so on.
Vending machines could be a $$ maker, too.
