The question of whether a website is necessary to earn money as an affiliate marketer is one that many newcomers to the industry ask themselves. Incidentally, it's one that old-hands in the business don't. That's because, in today's marketplace, the experienced affiliates know that they need a website.
Not very long ago, it was reasonable to expect a carefully researched PPC campaign to turn a hefty profit without having to use an intermediary website for an affiliate to refer customers to the vendor's site through - but the rules have changed, and if you find yourself competing against someone else who's trying to promote the same product at the same top-level domain, then you've got to outbid him or your ad won't be seen at all. This means that for PPC marketing, if you don't have a website of your own to drive PPC traffic to, your costs are going to rise considerably.
Having your own website, however, give you control over the content you're putting out there, and as we all know: "Content is King!" Without a website of your own, your voice simply doesn't have nearly enough volume to get heard online.
Your website is where you'll be able to engage visitors on your own terms - and if you've designed it to be appealing to potential customers for a particular product you're promoting, then you've got a perfect venue for discussing relevant matters and making a convincing argument that the product you're selling is the right one for your audience to purchase. Of course, you'd better be correct in saying this!
Without a website of your own, you don't have credibility as a marketer. And without credibility, why should anyone listen to your recommendations? The bottom line is this: you've got to get the attention of your market, convince them that you know what you're talking about, and then recommend their next move. Until you've got the respect and trust of your prospects, simply putting a link in front of them won't get enough of their attention to drive actual sales.
Besides, building a website of your own gives you an opportunity to express yourself creatively in a way that no other option can! You can design it any way you'd like, or hire a professional to make it look and function just the way you want it to. Since your goal is to attract visitors and convince them that buying the product you're promoting is the best move they can make to fill a need or solve a problem, it's simply a matter of ensuring that your website looks clean and appealing, contains valuable information in palatable chunks and is easily navigable. If you don't like the feel of your website, then it's likely that your visitors won't either - but adjusting it to your own tastes is the best benchmark for adjusting it to those of your prospects, provided you really understand them... And if you don't, then you've really got no business marketing to them in the first place.
You need a website to be successful in affiliate marketing. You need to develop credibility online, and you simply can't do that unless you've got a place of your own where visitors can get to know you as a professional.