Michael - I chuckled :) (saw the other one)
Really good question. I've been struggling with the flip-side of the same concern re: technical founder. I find it interesting how the biz and engineering worlds seem to foreign to one another even when we're doing the same thing.
First, I'd look for the same qualities and traits as in any other "what to look for in a cofounder" post. In my opinion the instant-no-go's occur when strategy, vision, ideas don't align. Plus, you obviously need to get along. I think that one is overlooked the most. If those don't happen, it doesn't matter if they're really good at what they do.
As for the skill sets in a biz founder, that's complex. While fundraising is important, I would suggest that you look for someone who doesn't brag about that or list it as the main thing they bring to the table. I'm a former VC, so it could arguably be my best strength, but I always side-step the "how are you going to get funding?" question because I hate the focus on it. Yes, it's important. But in the end, fund raising is only a byproduct of building your business engine the right way. It's much, much, much more important to know how to do that than be able to give a good story to an investor. Most investors aren't dumb, and prefer to have a less polished pitch with real, hard data and traction behind it than the opposite.
In that light, if I were you, I'd drill them on questions like: "What specific ways are you going to approach marketing? What steps does that involve? How do you measure a good campaign? How do you measure appropriate traction? When do you know if we need to keep tweaking our "business engine" versus applying resources to acquiring new customers?"
The point of these questions are twofold. 1) Avoid biz guys who claim they know what they're doing because "they just know" or "they've been doing it for 20 years." Same as an engineer. Not all engineers who have been doing it for a while can architect well. 2) See if they know how to build the business the right way. You should get answers that talk about some form of the following: LTV (lifetime value), margin, unit metrics, CAC (customer acquisition cost), customer retention. In short, the unit metrics of the business NOT total numbers "we need to get to 100 clients" or "we'll hit $1M revenue." This is a common thing VCs know and really good business guys know, but not a lot of people follow. No matter what business you're in - from a Mom and Pop sandwich shop to a multinational corporation - you do two things. You have way(s) of getting customers and you sell them something. As long as the first is less than the latter, you will grow. We express it as CAC < LTV (customer acquisition cost to life-time value), or in other words the cost to acquire a new customer versus the total profit that customer will generate over their lifetime of interaction with you. The higher that ratio is, the faster you'll grow. Aim for something like 2.5-3.5x. If you hit 5, call me up and I'll come running to join you and work for equity only :).
If you're potential biz cofounder doesn't reference any of that stuff, or doesn't really talk about it well after you bring it up, definitely time to move on.
Lastly I think Joseph was right - the best ones are biz guys who learn to code (a little) and can pull their own weight.
Hope that helps!