The core concept is to find unexplored industries or opportunities instead of chasing existing, well established ones. And, while I generally agree with that concept, in practice I have another theory:
pursue brown oceans.
What do I mean by this? A couple years ago I wrote about the phrase, "Where there's muck there's brass" describing the concept that, where there's dirty work to be done, there is money to be made. In this same way I think looking for 'ignoble industries" or "un-sexy opportunities" and seeing to dominate in that environment has a great advantage - a lack of competition.
Many of Benifactor's organizations are serving an unsexy market while repurposing best practices forged by sexy high paying markets. While it seems like it would be more beneficial to charge more or spend more glamorously, the trick of the situation is it places us in a red ocean, where we'd have to fight for every client dollar and thus counteractively become a less sustainable business.
Seek a segment within your world that is undesirable. Can you serve this segment exclusively and thus dominate that segment, happily knowing that no one wants to unseat you from your throne?