However, I think this just calls out all the open questions about this style of consulting and doesn't answer them. How does one get clients, how does one keep a steady income, how to invest for retirement, how does one convince clients you have the right skills, how do you know you have the rights skills, etc.?

He touches on some of these issues in a podcast interview with Radim Rehurek (of Gensim fame).

https://rare-technologies.com/rrp-2-john-d-cook-consulting/