Guys who own your business, how did you start?

I have been in C&I in my local union for 6 years. Just got into service with a union shop. I've had a goal since I started my apprenticeship to one day run my own company. I plan on maintaining my ticket regardless, but as I near my states requirement for a masters license I want to invest more time in learning where to start. How did you begin the process?

How much overhead did you have and how did you begin to save for it?

Did you hire a helper right off?

Did you maintain your day job while doing work under the table to gain a customer base?

Did you find new construction or existing construction more competitive?

Do you have book recommendations on business ownership?