A startup is tooo much work for a single founder. A team of 2 is ok (at least). You can hire someone on the technical side, But at least you need a dedicated co-founder on the business development side( yes BD is API centric now, not people centric, but there should be an Owner for this). This is required to scale up your business. The actual growth of the companty has to be on the side of Gaining more business from customers, Not on the technical side, That you can give to someone else who work for you. But in the beggining you need to know how to do it.
I recall it from his comments to ' YC Rejection Emails Are Out "
'A lot of people do that, and unsurprisingly some people (maybe all) working at YC do not appreciate it. Personally I would advise against it and think of a different way to get to the partners, n.b. Instacart, rather than show up to YC when everyone is extremely busy and putting YC staff in difficult positions." Now just think what he did with hedge fund manager ?.