3DPrinting

What value or expertise are you imagining that you would be providing that wouldn't be available to somebody downloading a model file and bringing it to a community library that has a 3d printer?

That's not a rhetorical question and the answer isn't automatically no. There is significant value in making things easy and convenient for people, and that is far from the only option available for you to add value. If you can answer that, and the value you are adding is significant and/or involves skills or tools or equipment that would not be readily available to most people, you may have a business case, but you need to be able to answer that before anyone can really assess the practicality of your dream. But you do have competition, a lot of competition, and that means you need to be ready to compete, and it's never going to be a sure thing. Statistically most startup businesses fail. But I think that's because a lot of them don't go in with a full understanding of what it takes to make an idea into a business. Money doesn't just fall out of the sky onto your idea. You need to work hard at it, understand the problem space and your competition, answer all sorts of difficult questions, build a name, clientele, reputation and brand and develop it into something that might become profitable (or might not) and whose profitability may suddenly change in either direction at any time depending on how accurately you are able to understand the constantly changing market conditions. And you need to be realistic about whether you think you can do this.