pg writes [1]:
YC grew out of a talk I gave to the Harvard Computer Society (the undergrad computer club) about how to start a startup. Everyone else in the audience was probably local, but Steve and Alexis came up on the train from the University of Virginia, where they were seniors. Since they'd come so far I agreed to meet them for coffee.
The talk he gave was How To Start A Startup [2]. The reason he was asked to give that talk was not because he had money, but because he was a Harvard CS alum who had built/sold a successful startup then spent the subsequent few years sharing his knowledge/ideas via books and essays.
The reason Steve knew about pg was that he had read/liked his Lisp book and read/liked his essays on Slashdot.
Money was a necessary but not sufficient condition for him to start YC. Nobody would have applied to YC if not for his books and essays.
[1] https://www.ycombinator.com/blog/the-reddits
[2] https://paulgraham.com/start.html