Given the size of this fellow's wares, I wouldn't be surprised if he starts things cooking on the go; certainly he wouldn't run awry of the laissez-faire attitude that pervades Beijing street traffic. And given the price (Y2 each, or about 25 cents), the business model must surely be sell early, sell often.
Sweet Potato Cart
Dongsi Nandajie at Dengshikou Dajie