I prepared a short wanted ad for my next venture with the kind help of my beloved partner. It got me to the first page of Youtube's search results for the keyword "find a cofounder" with just friends and family marketing. It didn't get me a cofounder. This indicates some relatively obvious conclusions: (1) There's ad arbitrage on Youtube, and (2) this doesn't matter if your target audience isn't looking for you over there.
Either way, here it is: