State sales tax: "Regular" or "Artists and Craftsman". A&C is only good for art and craft fairs - Regular would be for selling outside of art and craft fairs.
http://www.sctax.org/Publications/startbusns.htm
"If you sell arts and crafts which you make yourself, you can buy a special retail license for $20 to use for sales at arts and crafts shows and festivals. If you have no permanent retail location, you can purchase a transient retail license for $50 which will allow you to make sales throughout the state, but in only one location at a time."
License office is in the State Museum Building...
301 Gervais Street, Columbia SC 29214
Columbia Mills Building
P.O. Box 125
(803) 898-5000
City business license: possibly called a Festival license. According to a RAG member who recently got one... $25 for one year, or $10 per event. The one year license renews every Dec, and is $25 regardless of when you get it. Maybe cheaper to get the one time license. Price may be more if you do not live in Columiba. Cost of a regular business license may depend on the estimated amount of sales.
City Business License office...
1339 Main St, Columbia, SC 29201
(803) 545-3345