Once you sell the ad to a person, you can come back again each year and resign them. Or consider those folks who rate the campground, and who also sell advertising. Then there are RV caravans that need staff. Otherwise it won't work. You may decide it's better to sell a service rather than a product.
Telephone communications are difficult, as so many businesses require telephones.
Most campgrounds don't have telephone hookups. You'll probably be using pay phones a lot, and that's a challenge. Cell phones are wonderful, but if you use it exclusively for business you can generate substantial bills. Email is now really important, as more campgrounds are modem friendly. Trade shows, rallies, flea markets are everywhere.