For CPA you have to really pay attention and stay on top of it.
You should already know that PPV means that you are paying for people to view a landing page or a display ad, whether they click on the page or not. If it is displayed, it counts as an "Impression" and you get charged.''
PPC is different, it means you only pay if they click on your ad, it does not matter how many times the ad is displayed.
Either way with CPA you are going to pay for people to see your ad (or landing page).
You can certainly just add a cpa offer to an existing web page and hope someone clicks on it. I do, but it doesn't amount to much.
You have to find an "offer" to promote that pays you well enough to be worth the trouble. Then you have to find a traffic source that will convert in the offer.
These are two distinct separate things and you must keep this clear. You have to create an ad or landing page (which is called a "creative") to attract your customer. When someone sees your creative, it must spur some of them to click it.
When someone clicks on your creative they will go to your landing page. This is where the "sale" takes place. This page must convert the visitor into a buyer.
Sometimes the ad network will actually display the landing page directly eliminating one step in the process.
So you must make 2 conversions to get a sale, the ad must convert a visitor into lead, and the landing page must convert the lead into a sale.
You go to a source for traffic, (direct CPV, traffic Vance, Media traffic, there are tons of them and many are too small and have crap traffic. Ad Brite does not convert.), and you set up a campaign to drive traffic to your landing page by displaying your creative to their audience.
They will display the ads in whatever form you chose and charge you either for the view (PPV) or click (PPC)
The trick is that is takes time to test the traffic sure and see what they respond to. You must look at the demographics and find an offer that fits the traffic. If the traffic is older homeowners over 54 with small businesses, they probably will not respond to a victorias secret offer. AARP might be a better choice.
You must test, and keep the things that work, and continue tweaking things until to maximize your CTR's and make the most money.
You must also pay attention. Suppose you have a campaign running and making money with traffic source a, and traffic source "a" is selling a lot of traffic. Traffic source "a"decides to buy some extra traffic from traffic source "B" and throw it into the mix to have more available for their customers.
This new mix of traffic may well throw a perfectly good campaign off the rails, and it might not be making money any more. The longer it runs without being fixed, the more money you will lose.
You cannot do this and check everything each week to see how it is going. If you have a daily limit of $100 and do not find out about the glitch for 5 days that glitch will have cost you $500. Don't take many days like that to eat up your profit.
Golden rule: Test and track everything, never take your eyes off a running campaign.
And as everyone knows, never get bogged down in a land war in Europe.
Hope this helped