CPA marketing is when you make people take some action (e g. submit an email, or register an account, etc.), and you get paid for that.
It’s pretty much the easiest way to make some quick cash online with little to no money to invest.
You don’t have to be a guru to do it, neither do you have to run a site, although if you already have a site, you will do better when it comes to CPA networks’ approval and by applying quality tools like Babylon to help you earn extra money.
In fact, it is possible to make a lot of money with CPA marketing. I suspect that much of the big money is made by buying clicks to your CPA offers, like on social media sites that allow it. And if you can get a decently converting campaign that allows social media promotion. Many campaigns do not.
Publishers can earn thousands really and there are various CPA networks to choose from. You can earn by promoting various offers that are available on the network and you get paid when someone completes the required action for that offer.
Depending on what offer you are targeting, you might be able to convert high enough to make a profit by ranking well for your page with the offer on it. that is harder. I have done that, but it is a fair amount of work and does not work out so well if the company running the CPA offer terminates the offer.
So, the short answer is yes. The longer answer is it depends on how much time, effort and money you have to provide in order to get people to your offer display and convert at a high enough rate to make back your investment.