Yes, that's true Christina. There are job offering sites that requires money pre-installation before working with them. People really need to be vigilant these days. In my experience, Odesk and Freelancer gives security.
Start a business and do some local advertising? Unless you live in a third world country or can make do from mere peanuts the stay away from websites like Elance.
The problem with these sites is they attract a LOT of competition accross a BROAD range of skill levels from a WIDE range of demographics and locations.
This means that an inexperienced, slow typing student from India (no offence India but as a generalisation you do have a low income rate on average) who can feed himself for a week on US$20 can outbid you any day of the week.
Ok so I don't know if it's as bad as $20 but you get my drift.
In saying that it can give you valuable experience. For example design a website super cheap and not make any money from it but perhaps make a reputation; not to mention having an extra website for your portfolio. This is a hard road but then so can be starting on your own in any profession.
Best piece of advice if you are going to use these networks; Don't RELY on these networks. Use them for bread and butter maybe but look for other ways to find work at the same time.