Getting a shot at a coveted investment banking or finance job is a cutthroat, and sometimes controversial, business in China. Career consulting firms have mushroomed in recent years, enlisting what they say are thousands of finance professionals to help open doors to students who can afford it. Firms are charging $12,000 or more to help students land internships and eventually jobs at Wall Street powerhouses such as Goldman Sachs Group Inc. and Citigroup Inc.