Many of the most successful companies are way beyond product dev stage. Airbnb had launched ~6 months before they started YC. There are many other companies tha

Many of the most successful companies are way beyond product dev stage. Airbnb had launched ~6 months before they started YC. There are many other companies that are launched and gaining traction before they join YC, tikl, colorlovers are a couple of others that come to mind. The average age of YCers in my round was 26, and there were people that are below 21 and above 35 too. I think that has gone up as people now receive $150k extra and can reasonably survive even if they have other responsibilities. If you have the ability to move to Silicon Valley and are accepted in to both programs I think YC is a no-brainer (though I have done it twice so am highly biased).