That's something the startup I co-founded tried in the 2000-2001 timeframe. Back then, we did deals direct by scouting major sites that signed people up to multiple newsletters, and persuading them to add our newsletter(s) as an additional option. We then double opted in the resultant signups, and paid them for all the leads they produced. Rates varied widely from about $0.25-$0.75 per unique new subscriber (this was for business newsletters) and I remember spending hours poring through lists of new subscribers trying to assign them some kind of rough "quality score" to work out what we should offer the partner after the trial period ended (i.e. looking for how many name/address combos seemed like random collections of characters, "Mickey Mouse" etc.)
The company itself ran out of money shortly after the (first) dotcom crash, but we grew our list to over 1,200,000 unique subscribers in just over a year largely by the method I outlined above. If only we'd had something like Adsense (invented in 2003) to monetise the sites and newsletters, the company would still be around today!