Have you ever wandered into a quaint little antique shop and felt that thrill when you spot something truly unique? Well, if you've got a soft spot for vintage sewing machines, you're in for a treat.

SKIPTON — When marine engineer Jeff Greenblatt of Granite, Md., flips an electric switch, the museum comes alive with whirring belts turning shafts and rods along the ceiling and down to the floor.

With the rise of online marketplaces like eBay and Etsy, the world of antique reselling has never been more accessible or profitable. Whether you’re a seasoned collector or a newcomer to the trade, ...