You are building a campground. How do you expect to travelers to find you? If you advertise, the governing bodies are going to find you real quick (99.9 percent change one of your neighbors will turn you in, if nothing else). Then you will have to meet all the requirements for owning and running a campground. That will include zoning, drinking water requirements, sewage disposal requirements, taxation requirements, and a host of other rules and regulations.
You may be able to get someone to rent long term by advertising on either Craigslist or by using one of the VRBO type sites. You may even be able to fly under the radar that way. But you will have to price yourself below the market and take your chances with a renter that is very price sensitive. How do you plan on dealing with electricity costs? If you include it in your rents, you may find you vastly underestimate what some can use, especially if they don't care. If you bill it separately, that creates more issues. Are you going to take a deposit to insure payment? Are you going to create a separate power company account for each RV site? If you don't, and you meter each one yourself, there are laws in each state that govern what you can charge and what you must report.
Unlike selling stuff on Ebay, a campground is a visible business. You won't be able to just hide it and forget all the laws. Campgrounds are highly regulated. It is likely you will face more than a slap on the wrist if you get caught. And like another poster mentioned, once there is an injury on the property, all bets are off. Is a few hundred dollars a month worth the risk of losing tens of thousands in lawsuits and fines over an upset stomach caused by drinking water from a well that wasn't properly tested and recorded on the schedule set forth specifically for campgrounds and other public accommodations by the public health department?
