This is more of an opinion, I'm sure there are plenty of cases where the founders didn't know each other directly but were introduced due to common interests and it worked out just fine (My current company included). Yea, you probably shouldn't jump right into it, but I don't think it is a bad idea. Also - if you're sticking to your current network, I imagine the chances of finding someone who has more complementary skills is lower (ie: I'm an engineer & most of my network is engineers, what I'd really need though is more of a business/sales guy)