A dresser bought for $40 and a dresser sold for $400 can be the same dresser. The gap is a weekend of sanding and paint. Here's how furniture flippers turn skill, not luck, into margin.

Knife sharpening is a local, low-margin trade done off the back of a van. One company turned it into a national business by having customers mail their knives in. Same skill, no driving radius.

A dead 1950s radio is junk. The same radio, restored and quietly upgraded to play Bluetooth, is a gift someone pays hundreds for. Restoration turns nostalgia into a product.