I kept a Hobie 18 on Folly Beach for a couple of years...when looking at boats, having a beach dolly included with the boat should be a BIG plus. You'll absolutely need it unless you can find somewhere to trailer launch like James Island Yacht Club (trailer launching is still a PIA though). You can launch early in the morning at a couple of the parking / beach access alleys but you have to beat the beach-going cars because they'll block the access and you'll need to find a way to manage the early morning mega-toothed Folly Beach no-see-ums (less you eventually "go full monkey"). Death by no-see-ums sucks!

I also think you can still get permits to leave a boat on Folly Beach but you may need to be (know) a resident - I would do that again in a heart beat if I lived down there (just plan to have a way to haul sails, rudders, and boards home after each sail). Bury a couple of cinder blocks in the sand by the dune and run a cable through them before filling in the hole. You can lock the boat by wrapping the cable around an end of one of the beams and putting a pad lock on it. It also helps to keep it from blowing away in storms (but watch out for full moon tides).