I would agree with the other poster that said look for a mobile home for sale with the requirements for land that you want. It will end up being far cheaper and easier to tear out/remove a mobile home with infrastructure already in place than buying land and installing it yourself. Or look for land that already has septic and utils in place but does not have covenants to restrict an RV. But that will be pricey. Even in rural MD, build-able lots with septic and utils run about $100k per acre or more. Unless you have cash, most banks aren't big on lending money on land without proposed improvements to the property - aka - a house. An RV is not an improvement since it's a depreciating asset. Lot loans are pretty picky and have timelines for how long the property can remain vacant or devoid of an actual home.
Like I said earlier there are plenty of Farmers that would love to lease you a piece of land. In parts of varying counties all over MD there are fruit and grape farms that offer free land for the seasonal fruit workers to park their trailers. Most traditional small farms have a tough time getting by and would probably welcome the extra income.
Another other option is an RV park, but you won't find any with any sort of privacy.
