Rachel Ramos, who sells graphic T-shirts on Etsy from her home in Fort Worth, was considering closing her shop before she saw business unexpectedly boom last May. The shop brought her $25,000 from May through December, compared with $11,000 the entire previous year. She’s saving that money to buy a house for her and her two children. “This kept me from having to struggle as a single mother,” she says.
A less obvious, indirect recipient of her windfall: the states where her customers live, which can use taxes on her T-shirt sales to help plug the holes in their budgets....