If you are new to the industry then yes, pretty much essential.
I was working freelance full time for three years before I had chance to put something together I was happy with, but I was lucky that I had clients who knew what I could do and some contacts made over the years. It wasn't ideal and I could've done with something sorted out sooner.
I'm still not completely happy with what I have, a designers worst client is himself and all that, but at least I have something to point people too and, on occasion, that people find and get in touch via.