At the risk of sounding philosophical and all, I'll put out one opinion:
If you are thinking about starting your OWN business, you are contemplating stepping into one of the trickiest disciplines out there for making a living: Being an Entrepreneur. I would argue (carefully) that comes before machining skills, because it's the umbrella under which everything else falls.
Entrepreneurs are super-self motivated, take the initiative, and all of that combined with an innate ability to do so reasonably well or accurately. Anyone can suddenly jump up and "take the initiative" and go do something. That's no guarantee they do it successfully enough times it matters, that they had a rational approach to making the decision, etc.
On topic: IMO you want to start doing the Entrepreneurial footwork and start researching/evaluating what you are considering. That covers a lot of bases, but some of the first ones that come to mind are things like: What's the market? What are you going to manufacture, auto parts, low tolerance work, high-volume production vs custom short runs, die-cast & molding tools, custom gun parts, etc.? What manufacturers or suppliers (potential customers) are in the state you will be operating in? What potential budget do you have in mind? What are building/space/machine costs going to be, including tooling and measurement?
Start laying all that out in a Word Document, or Excel, or Powerpoint, whatever. That's your brainstorming knowledge-base. Incorporate advice from those more experienced, such as those here in this forum. There are decades, if not hundreds of years (combined) knowledge to be found on these forums. Consider what you are hearing, decide on what seems relevant.
Don't discount the idea of "measure twice, cut once" if you are thinking of stepping up to be self-employed or an employer. And you have to cover ALL the bases on that, not just the more obvious target of making stuff to sell to a customer.
Anyway, pretty general, thanks for the patience in reading this. Should you go for it, I wish you all the success to be had.
Take care.
