The focus should be what steps it takes to start a pinball business. Going from zero to pinball manufacturing = fail.

Build a related business first (machine operation, furnature manufacturing, game development, web/software development, or whatever). Those business will have a substantially easier time getting funding.

Have a 5 to 10 year road map that shows how that business will shift towards redemption and ultimately pinball manufacturing.

Pinball manufacturing is more complex then people give it credit for. None of the manufacturers started out just building them. They all had a successfull business (or 2) that fed pinball dev or outright bought an already operating pinball business.