I don't think its preferable to find a cofounder in an area that complements you. I think that this can be great, but what's most preferable is the right co-founder relationship. If the right co-founder is also an engineer, then that's fine. One of you should be CEO anyway, you can always hire business guys.
I think the classic mistake startups make is the duo where ones "business" and ones "technical" and the engineer ends up spending all this time building the product and the business while the business guy takes the CEO spot and controls something he doesn't understand. (assuming it's a technical business, if it's a non-technical business like a sport drink then a business guy for CEO makes sense, as sales are step key operational effort)
I think the classic mistake startups make is the duo where ones "business" and ones "technical" and the engineer ends up spending all this time building the product and the business while the business guy takes the CEO spot and controls something he doesn't understand. (assuming it's a technical business, if it's a non-technical business like a sport drink then a business guy for CEO makes sense, as sales are step key operational effort)