You can get Data Entry work on several legitimate online Freelancer Jobs Sites like oDesk.com, eLance.com, RentACoder.com, ScriptLance.com, GetAFreelancer.com.
They all provide you a platform to get work according to your skill set. Buyers post job requirement and providers/freelancers bid on the projects. Buyer choose the winner and awarded job to him.her. He/she has to complete this job in promised time frame. After successful job completion buyer release payment, Freelancer Jobs Site charges their fee and pay your earning to you.
Its really hard to get your first project initially but continuous efforts deliver you positive results. After getting started, buyers know you and can award projects directly to you. As you got work, your portfolio and reputation also increases, and more buyers attract to you.
oDesk is recommended for the beginners.