If you are buying an existing business in the U.S. to get an E-2 Visa, there are a number of documents that will be requested to demonstrate that the business your are purchasing will qualify you for an E-2 Visa.  Some of those documents are:

Occupational license
Business license/business permits
Sales tax receipt
Utility/telephone bills
Business transaction records
Current/commercial account statements
Letters of credit —
Invoices from suppliers
Advertising leaflets
Business brochures/promotional literature
Newspaper clippings

The business must be a for profit, bona-fide business.  It must meet all the legal requirements in that state or region.  It cannot be a passive investment in stocks, bonds, or real estate, since those are not considered active investments.