The oversized shed at the back of this property in Highland Park, Los Angeles, was a bit of a mystery. It had stood for 90 years, filled with tree trunks on one end and interesting antiques on the other. The current homeowners, a television writer and a musician, discovered that plans for the shed had once been filed, yet the city didn’t officially recognize its existence. Despite its state of flux and disrepair, the couple was sure about one thing: It had potential.