Anyone working in the design industry will come across many kinds of scams in the job market today. Always bear in mind at least these three little tenets of honour out of respect for yourself and the craft.
#1: A freelancer will not touch dodgy potential clients
You do not always have the luxury of face-to-face communication. However, in this line of work you can tell all you need to know about a person or business from their initial written output.
You will all occasionally fall on quieter times on the work front, but do not respond to potential clients who write poor grammar or in all caps. They are probably a crook who will screw you at the first given opportunity.
#2: A freelancer will under NO circumstances provide a business any form of practise assignments
Do not be fooled into "demonstrating your skills" by sending some assignment or entering a poorly known competition. This is a scam used by many small businesses into getting a free new logo or other content. Nothing prevents them from using your designs and/or copywriting. A good portfolio does this trick: hyperlink 'em instead. That will tax them on the ripping front to at least some extent.
#3: A freelancer will not pay to get paid
Do not use your precious PayPal dollars to fund "job service" rip-off schemes. They are as worthless as they are plentiful. Also, anything with a beta-logo and taglines in the mould of "revolutionary new community/service/platform" is an evil, pointless excercise in futility.
That's it. Now get out there and make a name for yourself.