If you get a pressure canner, don't get one with the pressure gauge on it. Those things are notoriously unreliable and get worse with age. Those are the things that cause pressure cookers to explode.
Get one with the jiggler.
Also, make sure you get a good resource book for learning proper canning techniques. Auburn University in Auburn, Alabama has a book that is considered the best work on the subject. You can order it from the university's web site, I think. It's worth the money, for sure. Auburn has a department of food science, so that makes sense.