Can you say more about how someone renting a botnet would generate (illicit) revenue through click-fraud?

I understand how a botnet could be used (and highly effective) to generate fraudulent clicks, and I understand how fraudulent clicks create a problem for an advertiser or a pay-per-click advertising company. I also have a reasonably good understanding of the more well known things botnets are used for.

So I’m the guy somewhere in Eastern Europe, I pay my friend to have his botnet run up tens of thousands of fraudulent clicks on some unsuspecting merchant’s google ad – how do I generate income from having that done?