There’s lots of folksy wisdom out there about what to look for in a spouse: phrases like ‘opposites attract’ and ‘the couple that plays together, stays together’ instantly come to mind. And surprisingly, many of these same qualities apply to the search for a business partner.

I’ll dispense with the shortlist of desirable traits, because it would include words like ‘trustworthiness’ and ‘integrity’ — qualities that are as obvious as they are timeless. And I’ll give you the benefit of the doubt and assume that if you’ve made it this far as an entrepreneur, you know what these things are, and how to identify them in a prospective partner. So let’s dig in a little deeper. What does an ideal business partner really look like, beyond these résumé-ready descriptors?

Someone who provides an answer to your limitations
Your business partner should be someone who completes, or at least adds to, your skills and knowledge. Not to put too fine a point on it, but it just doesn’t really make sense to collaborate with someone who could be your twin. Like a well-chosen presidential Cabinet, or a team of astronauts tasked with exploring space, a business can only thrive when you have a selection of people with different — yet complementary — skills. In other words, people who can do the things you alone, cannot.

See also: The most important relationship you will make in your career

Someone who knows when and how to challenge you
Take a good look at your closest friends. Do you surround yourself with ‘yes-men’ (or women)? Do they refuse to challenge you because they don’t want to risk conflict? If so, this is not the sort of person you want to run your company with.

Your business partner should be someone who isn’t afraid of engaging in the occasional heated, but ultimately productive, debate. Most of humanity’s greatest achievements were made possible, at least in part, by conflict: arguments between people who shared a vision, but differed on the particulars of the execution. A good business partner will support you in your decisions; a great one will have the courage to speak up when there might be a better path forward.

Someone who has the right motivations
There’s a cruel irony at work in corporate America, and it has to do with the influence of profits. It stands to reason that just about any modern business would cease to exist if profit were no longer in the equation. And yet, we see time and again what happens to the company that chases profit the way Ahab chased his whale in Moby Dick.

I’ll put it another way: too many people forget why they went into business in the first place. It needs to start with the desire to build a world-class service or product, which is simply a roundabout way to touch and improve the lives of the people around you. You need a business partner who respects the idea of profit, but puts it after more important motivations, like a passion for doing quality work and improving your little corner of the world. In my experience, profit takes care of itself if passion—and not money—remains the center of your universe.

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