You keep 100% of your income, but employers do set a nominal amount of credits (usually $1-3) per bid on their projects. This is really beneficial for both parties. If you've ever used other freelance marketplaces, you'll know that it's difficult to get noticed when you drown in a sea of bids. And usually, the freelancers never even read the project description. The bid fee ensures that freelancers are serious and qualified for the job, reducing spam and making you much more noticeable.