There are many different ways of investing money, but when you invest in your own business, you're really investing in yourself, in your brand.  This is the exact opposite of a passive investment.  Quite the opposite.  If you're in between what you would like to do, consider starting a blog, like this one, and put your ideas down for others to give input.  In fact you can even use a blog to start a business.  If you would like to start a business, and you like to write, this is as passive as one can be without getting a real job.