In general don't start a startup you're not willing to work on for ten years.
If someone is choosing between joining McKinsey or your startup it's very unlikely they're going to work out at the startup.
You're either not hiring at all or it's probably your single biggest block of time.
Experience matters for some roles and not others.
Developing a personal connection with anyone you're trying to do a big deal with is really important.
Many of the best YC companies have had phenomenally small number of employees for their first year, sometimes none besides the founders.