Vaguely relevant: I was recently in New England (I live in Australia), and ended up spending a night sleeping in the back of my rental car, on a private golf course (it was dark). Police arrived in the morning, questioned me, scanned my ID, sent me on my way (well, told me to go sleep 50 metres down the road in a "public" area).

Moral of the story: Even if you get found sleeping on someone's private property, and the police get involved, 2 years in jail is probably unlikely. This was Maine though, not SC.