Half a million dollars and nearly four years into his Los Angeles-based cannabis venture, Donnie Anderson had no shop, no prospects and a mountain of debt. With financial help from family and friends, Anderson rented a $6,000-a-month space in January 2018 for his new cannabis retail shop. He kept paying the rent as the city’s permitting process dragged on. He bought cabinets and other equipment as he waited. And waited. Sick of waiting, he’s selling…