A few directions to chose.

If Pinball Machines are in your life for Income, you should invest a few years learning to work on them. Experience.
Whether you become a large Business, with many of techs, or you are a one man repair person, youll need this information first.

While learning, you can decide if you want to be an Operator, Restorer, Distributor, Repair, or at the sides...Mods, Parts, extras, or
behind the scenes in Art, development, or other. Business classes, and other education, along with your work.

Your balance is between passion and money, as is everything.