You're going to learn a heck of a lot when doing a business, regardless of what that business is and regardless of what your present skills are.

A friend of mine (Jay Winder) often talks to me about product/founder/market fit, and I think that is potentially a more powerful thing than merely having skills alignment. When you're "the right person to do this" (because of longstanding obsession with the domain, pre-existing connections, some "unfair advantage", etc) you're more credible to clients and investors and you tend to get even more credible as you execute than you would in the baseline case.

Skills you can learn (surprisingly quickly) and/or hire for. An underappreciated bit of starting a company: you're going to spend so much time on this problem, more even than many people who encounter it professionally, that you'll relatively quickly be one of the world's experts in it. This is a surprising insight but I think it rounds to true: you're not aiming to understand an entire field like e.g. dentistry. You're aiming at 5% of the operations of a particular employee at a dentist practice. How many years do you have to focus on that to have spent more hours on it, and more considered hours, than every person thinking about that problem? Probably something like 1, 1.5, 2 years, right?