It's not just a case of writing 50k words, though; there has to be a story with a beginning/middle/end. I did it last year and hit the target. Half of it was junk,, but the rest of it was the bones of a story that I can build into a novel. I'm still working on it, very slowly because I have other interests in my life now and I gave up dreaming about being published ages ago, so there's no rush.
If you can think of it as splurging out the basis of a plot, then it's well worth doing - and it's enormous fun. Stay out of the forums, though... they are deadly serious in there!
Dee
<Added>Good luck, Tanya!