My co-founder and I (we run a smallish, growing business, but not what would typically be called a "startup") met at high school (aged 11 or 12). We then went t

My co-founder and I (we run a smallish, growing business, but not what would typically be called a "startup") met at high school (aged 11 or 12). We then went to different colleges, shared a house after university, worked for other people for a bit and then started our company. I can't imagine founding with someone I didn't know incredibly well - though I don't think you need to go as far as we did and choose your best friend. In any case, as others have said, make sure that your friends are actually good at stuff. I suspect this also only works if you have the kind of friendship that is built on talking business all the time too. It is actually the foundation of our friendship in many ways so I think that reduces the risks involved (though not to zero, obviously). There is clearly some personality-type stuff going on here too though - my wife was also my friend for years before we got together...