Search engines derive income from advertising. Venders are charged each time a potential customer clicks on their ad.
When I joined HubPages I set up an account with Google. Whenever a potential customer clicked a Google ad attached to my article, Google would reward me with a small payment.
From time to time, Google will offer me one hundred dollars worth of free advertising. It’s not a bad idea; I could always cancel if their efforts fail to increase book sales. One day I might give them a chance.
If you test this method, please send an email to email@example.com documenting your results. Then I’ll update this page to reflect your opinion of Google based advertising.