This mirrors a lot of my own feelings (being a single founder myself). I originally applied for YC for the W11 round, and I rushed to find a cofounder before applying (even wrote this for HN: http://www.limedaring.com/technical-co-founder-wanted-for-di...)

I spent a few weeks "interviewing" cofounders and working with a few, before choosing one and starting to build a product and applied (and scored an interview) for YC. But during that time I realized that this person was not the person I wanted to start a startup with. Thankfully we didn't get in, and parted ways. Since then, I've decided that having a partner would be awesome but I'm not wasting time looking for someone (especially with the very small pool of people that want to work on wedding startups)... instead focusing on building as fast as possible on my own (product: http://weddinglovely.com, launched and making small bits of revenue).

I'm applying again for YC this round as a single founder, and I would encourage people not to rush out and find last minute cofounders just to apply. Spend time now finding a cofounder, then apply for S12 after a good few months of working together — and if you can't find the right cofounder, then start building yourself (especially if you're not technical).