ff.net accounts are free. You have to have a password to get into your account, and it is best if you keep that a secret. Just like with any password you might have, as a safety precaution.

There are a lot of good stories scattered around ff.net. You just have to be willing to sift through the not-so-good to get to the good stuff. I don't have the time to do that anymore, so I've never explored any category except the Hardy Boys.