I've read some newspaper articles from that period between South Carolina declaring secession and the beginning of hostilities in April. The people to whom you refer were moving in to take advantage of the opportunities that were happening in Charleston. Hotels were booked. You could not find a room in the city. Warehousing was being constructed, and the business outlook was massively optimistic. Shipping companies were relocating to Charleston, and a whole host of Northern based industries were looking to get in on the action.
The money would have brought them.
But they would have remained Northern owned. The profits would have gone North.