What I find most often is that aspiring freelancers/consultants don't realize 1 important fact: Freelancing/consulting is harder than a 9-5 salary job, in every way. If it's one theme that rings constant among freelancers or consultants that I've lent an ear to, it's the "I thought it would be easier" sentiment.
And that supplements the point made in the article. So many developers think their craft is enough to succeed as a freelancer or consultant; the truth is quite the opposite. A business' success depends on marketing and selling their services, and that's what most (if not every) developer underestimates when they start a freelance or consulting business.
To help combat that, I also advocate the gradual approach. Take a full time job in the industry for a few years first, then build up your freelance/consulting business on the side until it becomes sustainable.