If you're reading this article, most likely you typed in "free affiliate program" or something similar in one of the search engines. Now what I'd like you to do is step back for a moment and think about that search query. Why did you look for free affiliate programs? Could an online marketing program be anything other than free?
The way online affiliate marketing works is that you promote someone's (the merchant's) products or services. If you generate revenue (or a lead) for them, you get compensated. If you generate nothing, you get nothing. As simple as that. Since there is absolutely no penalty to the merchant if you don't sell anything for them, they should never ask anything of you. You should never have to pay for the 'privilege' of promoting their products
Affiliate program or Ponzi scheme?
Unfortunately, in the real world there are many non-free affiliate programs. Typically they charge you a one-time signup fee, or, more commonly, require you to purchase their product yourself. While there is nothing wrong with buying for yourself the product you promote--it might be a really good product, and if you own it you'll be better able to convincingly sell it to others--this should never be mandatory. From a business perspective it doesn't make sense. Unless...
Unless the merchant's business model is based solely on selling his product to (aspiring) affiliates. In this case the affiliate program works like a pyramid scheme (or Ponzi scheme). See, the merchant initially sells his product to a few super-affiliates and promises them fat commission cheques if they can bring in new affiliates. They start touting the product to others, showing just how much money they are making with the program. Those others become affiliates as well, making the cash register rinkle for the merchant and the super-affiliates. Now the new affiliates have to find yet more sub-affiliates to sell the product to, and so on. As anyone can see, the market soon runs out of prospective affiliates and the last ones to join end up buying an expensive product with no means of making their money back.
Example of a non-free affiliate program
An example of this type of scheme is the affiliate program offered by the Empower Network. (Note that I am not an Empower Network affiliate and do not endorse their product or their business practices in any way!) They sell making money with your online business courses (the kind of stuff you can read for free on Affiliate GOOD) ranging from $25 a month to $3,000 (I think... they don't actually disclose the price of their most expensive product before you've bought one of the cheaper ones). They show prospects of making thousands of dollars as an affiliate, but of course, to become an affiliate you have to buy their product first.
Surprisingly enough the Empower Network discloses the income of their affiliates (see this page). As you can see, 86% of their affiliates average less than $100 a month on the program, while paying $25-%100 a month for the 'amazing' money making course they are getting. And if you read the fine print, you can see that these stats only include affiliates who have made at least one sale in the past 30 days. I can imagine there are thousands of affiliates out there on the bottom of the pyramid who are not making anything at all.
Only do business with truly free affiliate programs
The lesson we can learn here is that you should only use a truly free affiliate program to make money with your internet business. A good and honest merchant has no reason whatsoever to charge you for the 'privilege' of promoting their product. If you like what they offer and think you can benefit from it, by all means, go ahead and buy it. You'll be a better salesman for it. But never pay just for becoming an affiliate.
All the good affiliate programs I mention on this site (see the affiliate program review directory) are completely free to join. Some offer products that are really amazing and I would definitely recommend buying. Others are simply good money makers for you as an affiliate. But all of them have in common that they are truly free affiliate programs.