This one that I have quoted below is interesting, and what’s weird, is only two years ago I would have disagreed with this idea of having a cofounder. But I think it’s really important, now.
Not having a cofounder is a real problem. A startup is too much for one person to bear. And though we differ from other investors on a lot of questions, we all agree on this. All investors, without exception, are more likely to fund you with a cofounder than without.
We’ve funded two single founders, but in both cases we suggested their first priority should be to find a cofounder. Both did. But we’d have preferred them to have cofounders before they applied. It’s not super hard to get a cofounder for a project that’s just been funded, and we’d rather have cofounders committed enough to sign up for something super hard.
If you don’t have a cofounder, what should you do? Get one. It’s more important than anything else. If there’s no one where you live who wants to start a startup with you, move where there are people who do. If no one wants to work with you on your current idea, switch to an idea people want to work on.
If you’re still in school, you’re surrounded by potential cofounders. A few years out it gets harder to find them. Not only do you have a smaller pool to draw from, but most already have jobs, and perhaps even families to support. So if you had friends in college you used to scheme about startups with, stay in touch with them as well as you can. That may help keep the dream alive.
It’s possible you could meet a cofounder through something like a user’s group or a conference. But I wouldn’t be too optimistic. You need to work with someone to know whether you want them as a cofounder. 
The real lesson to draw from this is not how to find a cofounder, but that you should start startups when you’re young and there are lots of them around.