Look for somone who can stand with the company even in worst time. Also, find someone with strengths not same as yours. Like, if you're good in tech find someone who's good at management and sales. This way you both can balance and work won't conflict with each other.

Apart from the above, also look for a person who calls spade a spade - take it with a pinch of salt for the long term. You don't necessarily need a Yes person but someone who can counter an opinion with facts - family, friends, strangers.

Business Development Manager

Angel.co? You can specify looking for a co-founder. Have seen a couple of people start up using Angel

Software Engineer

Assistant Manager

Generalist

You can maybe checkout the Cofounder app - https://play.google.com/store/apps/details?id=com.cofounder.android 
  
 Hearing a lot about it these days!

Co Founder