The Four Types of Business Ideas

Correct me if I’m wrong, but all business ideas seem to originate from a finite group of categories; each having an unique trajectory to fruition. I would arbitrarily describe these categories as A, B, C and D. Category A - Solve a known problem A client comes to you with a problem, and you solve it in exchange for compensation. There is little to no guesswork as to whether there are paying customers or anyone who actually wants what you’re building.