It turns out that, even today, nearly all of the big checks in the ad industry are still being written for big, broadcast marketing efforts (television ads, radio ads, billboards on the side of the highway, etc.). You might find this surprising given all of the conversion-based marketing channels that have popped up over the years. Advertisers no longer have to worry about not being able to track their ad spend. Marketing has become measurable. Google can tell you how many leads they drive to you so the problem of wasted ad spend should be over. So why are marketers continuing to spend on the big, hard to measure stuff? In many cases, the reason is that lots of ad buyers are really out to do one thing: avoid getting fired. So they’re very reluctant to take a risk on something that can be tracked. Many would rather their boss see a beautiful ad on the highway on her drive to work as opposed to a report showing that the new marketing campaign failed to drive a positive ROI.
With that in mind, in your early conversations it's important to understand where your prospect sits on this topic. My take is that high performing companies and individuals want to measure their performance and the performance of their vendors -- so that they can intelligently expand (or limit) partnership growth. If they are reluctant to measure success, they may not be the right partner as growing the relationship will typically be much more difficult.
Be cognizant of the fact that your partner might be hesitant to be measured. Try to get them to open up a bit on the topic -- it'll help you get a better sense of whether or not they're the right fit.