Paying your mortgage off early, is it a good idea?

Many people see having debt as solely a bad thing, but in this Business Insider article the author Mr. 1500 challenges that notion with an example of how he invested extra money instead of using it to pay off his mortgage early and ended up coming out ahead. 

Though 3.5% interest may seem like a lot, and the dollar amount of interest over the life of the loan might shock you, this article will show you how investing that money could lead you to realize better returns.

I'm worth 15 million and I'd never recommend paying off your mortgage early