Tangential question: How do founders typically retain control of their company? I've specifically been told that it's wise for one person to own 51pct of the company and be CEO. However, with 20 pct of equity for investors and 10 reserved for future employees, this doesn't seem to leave much for cofounders who are potentially putting as much skin in the game as the CEO.
If you have a working product and ideally money coming in, the early negotiation leverage changes dramatically. You can skip the seed round entirely, because you've already seeded the project. You can usually get a very good valuation on Series A, since your metrics look great and every VC wants a piece of you. You can negotiate to give away very low equity stakes in later rounds, since at that point you seem like a sure thing.
The flip side is that most side projects don't go anywhere. You need to be both very dedicated and very lucky to strike it big without investment.