The path to success varies widely by individual and industry. It relies on having the right resources at the right time, and the right talent to guide the effort on the right path. Some roads were fast, some slow, some rocky, and a few smooth. So there's no one answer.
What I can tell you is that there are six fundamental business skills every business requires: 1) marketing, 2) sales, 3) organization, 4) efficiency, 5) people, and 6) leadership. No individual will ever master more than two of these skills, so you will always rely on others (employees, advisors, contractors, etc.) to fill in the skill gaps. The first steps taken are research and planning. You can't skip these, and you need to do them yourself as a founder. The next steps depend on what you discover. The process of building a business requires many rounds of discovery and constantly evaluating your assumptions.
What happens next isn't some magic repeatable formula. There are to many dependent elements. If it were a formula, there would be one book and everyone would follow it.
It has almost nothing to do with solo versus co-founder status. You will always need at least two someone elses at some level to master the six skills and support you, if not more. They don't have to be founders, but you will need them.
Thanks for your answer. You are right, it depends on so many things, their current skills, network and kind of effort involved.
Every startup does not need a co-founder, but the sole founder has to be exceptional to pull off a solo act.
Co-founder doesn't have to be at the startup the first day. Y Combination define a co-founder as someone with at least 10% of the shares. (I was surprised to find that out) so if we use that guideline, then anyone with 10% of the founding stock, with the implication that the stocks are given out base on merit, is a co-founder.
One thing to be concerned about, if you cannot share your vision with someone and convince them to join your team, you might have the same problem with customer and investors. It maybe your vision is fine, but your communication are unequal to the vision.
Even the great solo founders had to convince people to follow them.
Yet there are so many benefit of having co-Founder but it doesn't mean you chose your Co-Founder just because you need one but you chose one because he/she qualifies to be one and you guys can have good boundings etc. Trust me having no Co-Founder is better than having bad/incompatible Co-Founder.