I first started writing on Both Helium and Triond: http://www.triond.com/rw/356296
when I started my freelance business. Both of these websites are great to start off with, and it can make it easier for the writer to make money right off the bat.
I say first start your portfolio with either by writing about any subject, or choosing subjects that are being searched for everyday online. Then, learn all about marketing and how to use Social networking sites to your advantage.
I highly enjoyed writing online because it really gave me the pull that I needed to make money for myself.
Once you get the hang of it, its amazing!