Commission Junction (CJ Affiliate) does not charge upfront fees for joining. You can sign up as an affiliate for free. However, CJ Affiliate takes a percentage of your earnings as a commission. The commission rate varies depending on the merchant. Each merchant sets their own commission structure. You should review the terms of each program before joining. Some merchants offer a flat rate per sale while others offer a percentage of the sale. You can earn more as you generate higher sales. CJ Affiliate also offers tools and support to help you maximize your earnings. Make sure you read the program terms.