What is the transition from full-time employee to full-time consultant actually like?

In an era where more people than ever want to be their own boss, many people are trying to make the transition from a side hustler to a full-time entrepreneur. Even with the increased interest, the transition is still shrouded in mystery.

When is the right time to transition? How much money should my business be generating before I leave? How do I let my employer know I’m leaving to do my own thing?