Manhattan Business School · Big Ambitions wiki

In order to expand your business empire, you'll need to take some courses at the Manhattan Business School.

You must complete the courses in order

Basic HR - Recruit employees from Anderson Recruitment Corp. or City Workforce Inc.
Market Demands - Open and run multiple retail businesses
Headquarters - Open and manage your Headquarters to import retail goods and manage HQ personnel
Office Businesses - Open and run office businesses like Event Planning Agency, Graphic Designers, Law Firms, Travel Agency, and Web Development Agencies
Product Manufacturing - Open and run Factories to manufacture your own products

From the game's own in-game help (Big Ambitions by Hovgaard Games), as shipped with the game. Big Copilot reads your save and shows your businesses, supply and staffing against it.