Remember, starting a turnkey business is just the first step in your journey as an entrepreneur. Its success depends largely on how much time and effort you put into it. Choose a niche you are familiar with, conduct market and competitive research, buy a company that aligns with your goals and then take the steps needed to turn it into a successful venture.
In the case of cost per mille/click, the publisher is not concerned about whether a visitor is a member of the audience that the advertiser tries to attract and is able to convert because at this point the publisher has already earned his commission. This leaves the greater, and, in case of cost per mille, the full risk and loss (if the visitor cannot be converted) to the advertiser.