I live in Charleston. Well, Daniel Island in Charelston harbor. The personal property tax is 10% per annum, but it is technically not that simple when the calcualtion goes into millage. But the bottom line is a lot. If you think yoiu might be liable, call the assessor of the county. Never rely on anyone else. I used to have a sailboat insured for a quarter million, and the two counties owning Charleston harbor (I've lived in both) wanted $6000 annually for the privilege of tossing out my anchor there. Kept the boat in VA as I do my current one.
Charleston is and has become a popular winter - over locale. It is not cheap, but the weather is mild and there is a lot to do and see and all is convenient. Good connections. Good everything. But do not stay over 180 days!