I’m not sure what you mean by that. But generally we get about a 30-50% ROI on our native ad campaigns once they are optimized, and most affiliate networks pay weekly if you produce significant revenue. We do better than most because I wrote some clever stuff to identify sites that were sending us mostly bots/bad traffic and automatically blacklist them from showing our ads. There are a ton of these in the native ad space.

I just suspect most of the trick is in generating demand, not finding it.

There are evergreen affiliate niches such as weight loss, hair loss, erectile dysfunction, etc. Aging, bad genetics, and poor lifestyle choices generate the demand for us. Making money in these niches is generally as simple as placing ads on sites where people that belong to certain known demographic groups visit, and reducing fraudulent traffic by as much as possible.