"Living the dream." To many entrepreneurs, that means running and growing a business they love while also having enough time and freedom to live the type of lifestyle they've always wanted. One way to live your ideal lifestyle is to start a business around a passion you have.

But starting a company around something you're passionate about isn't enough. Lifestyle entrepreneur and online marketing expert Lewis Howes says whatever you do -- no matter what your product or service is -- it's critical that it solves a real problem for people. 

Otherwise, your business won't be sustainable.

Related: Set Your Own Rules and 'Live the Dream': A Google Hangout With Lewis Howes