How do you find a co-founder?

I’m currently building an mobile app. Launched MVP, already got a couple of customers and I would like to keep going. The only problem is I do everything all by my self. When I focus on technical aspects I don’t have enough time for marketing and sales. Therefore I’m seeking a co-founder who can take care of this part of the project. What is your experience with looking for a co-founder? What is best way to find someone good and more importantly how to verify if he/she would be a good match?