True Date Entry positions are rare and very tough to come by. The best advice I can give: Don't ever pay an up front fee for a data entry position. If they try and charge an up front fee, chances are it's a data entry scam.
Data entry jobs online are simply typing ads for other companies (affiliate programs) and then when a sale is made, you earn a commission. Many people think that they are real typing jobs that you get paid hourly. It is not.
As Tal said above, most data entry jobs online are basically training programs for affiliate marketing. They are not all bad and you can learn a lot from the information. Everything you learn online you will have to pay for one way or another, either with money or your time.
There are actually real data entry jobs out there on some of the bid for work systems. Each job is usually temporary but you do get paid based on what you bid as your hourly rate.
I don't disagree LTWeb. There are some legitimate ones out there. But legitimate data entry jobs will never charge you an up front fee.
KeyForCash is a legitimate data entry job online. The drawback is it's very competitive and the pay per keystrokes is low unless you can really type fast with little or no errors.