Like many sci-fi movie societies, Divergent's faction system does not require such businesses. Since there is a faction that produces food and goods, and provides services (Abnegation), everything is covered. Any service only used by one faction is taken care of within that faction's hierarchy. There is no need for retail-like business or the creation of profit.
The idea itself could be sound in practice, assuming each faction does its job; a lot of intermediary occupations which people are overly used to today would simply be nonexistent.