To get to that point, you have to do a lot of the things bigger companies have to do. Those things just tend to be less complex and you have fewer people to do them. Accounting, sales, engineering, marketing, etc., etc. all exist, to some degree, in a two-person company. At first, you learn to do them yourself. You'll probably suck at them. It's okay. They all have some degree of a feedback loop. If you're open, you'll figure it out. Eventually, with success, you'll hire other people to do them.
From there, you can get access to a great network by doing an incubator as someone else mentioned, or by just getting out there and talking to users (do this day 1). But you're worried about years 2-4 when you haven't even started year 1 yet.
If you want to discuss in more detail, I'm a founder with a product in banking that's been moderately successful. Email's in my profile. Feel free to reach out.
The main thing is you have to start, get a team to follow you somehow, and get a reference client live and on the record using your software to solve a huge problem. Consider YC or techstars for your first $$$ investors. Some may tell you the negative of working w them but they’re deeply wrong
I don't know what you're asking with the rest of your question.
I'm in the position of believing I have "1 thing right." I worked in an industry (banking) with a serious software problem and one particular vertical that I'm confident I could build a good product for. I was in a position to evaluate all of the major vendors that would be my competitors, and I'm confident that I could get one particular thing very right. Ths problem is that I have pretty much no idea where to go from there. I've never started a company, I didn't even study business in school. In my career so far I've pretty much done two things: I got very good at that particular aspect of banking, and I taught myself to code and now do it professionally. But I'm so aware of the gap between my own knowledge and the skills required to run a business that I wouldn't really feel confident trying to go get investment money (and wouldn't know how to begin even if I thought I could use it responsibly). I guess what I'm trying to get at is: once you have the one thing, where do you go for help with the thousand?