You don't need to be a millionaire to become a business investor; you only need to have enough money to make a material difference to a startup company that needs it. We live in the age of crowd funding. There are thousands of individuals and businesses out there, asking the world for funding to support their new idea or product. Often, they'll offer a stake in the company or a percentage return on investment in return for your support.
The key is knowing which firm to back. A lot of technology companies or new inventions sound exciting, but either never see the light of day or don't work as they were supposed to. Look for start-up companies that operate in industries which you know always make money, or established companies that need a little capital for expansion. They may not be exciting investments, but they're more likely to be reliable. Owning 5%, or even 1%, of the right small company could mean your share is worth millions when they're bigger.