This works, but its tough. You have to send out COUNTLESS emails or pms. I say you make a webiste or buy a good-looking logo website from flippa.com and when you send the email (make it look professional obviously.) Say you have been doing it for a few years blah, blah, blah, send him some samples and say I know exactly how to complete your order. Use multiple sites not just odesk, use Craigslist and other sites like them. Now, i would say fiver is fine but if you want repeat customers use someone else who will charge 20$ instead of 5$ and will probably do a much better job.
Food for thought: your basically robbing people because they have a lack of internet marketing knowledge but hey you do what you got to do right?