Hank most of those are scams so beware. If they don't ask you to register then it's more likely to be legit and there are free ones out there. I bought a book on H. H. Windsor's furniture plans that had been published in Popular Mechanics shortly after 1900. Not long after I found the same thing on line for free. I'm guessing the copyrights ran out decades ago. Truthfully, if you see a picture of something you like, you should be able to reproduce it within reason (I have no hopes to ever be able to reproduce a Roentgen piece because I lack the skills). The Windsor furniture was meant to be produced by novice woodworkers with moderate skills from lumber available at the local lumberyard so the basic design may not be something you want to build but they can be a great source of inspiration. Gene Howe recently built a chair in that design but his had curved arms, something you would never see on an original.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.