Well, the livejournal site can look professional - you could try to make it look a bit less... "livejournally" and more customized, if you see what I mean? Since LJ offers practically limitless customization and why pay for something if you can get it for free?
Also, at www.dot.tk
you can get free domain forwarding, so you could have someone go to, say, www.knitting_panda.tk
and they'd get taken straight to your livejournal so they'd never know.
And lots of people have very successful LJ businesses, so don't fret ^_^