Let's talk about canners. Aside from jars and lids, the canner itself is your first big monetary investment. There are pressure canners that have a rubber seal, pressure canners that don't have a rubber seal aka "metal-to-metal", and boiling water bath canners.
The above is an example of a pressure canner that has a rubber seal. The cons are that the rubber seal will eventually need replacing. The pros are that this kind is more affordable than the metal-to-metal pressure canners. This is the kind that I have. Learn from my mistakes and get a big one from the get-go, otherwise you end up getting a bigger one down the road. Canning just four or six jars at a time gets old when you have a lot to do.
This is an example of a metal-to-metal pressure canner. The pros are that they have no rubber seal to wear out and need replacing. The cons are that they are much more expensive than the other kind. Expect to pay $200 and up for one of these. I would like to have one myself, but it's not happening anytime soon.
This is an example of a boiling water canner. In my opinion, this is a waste of money. The reason is that if you have something you'd really rather put up using a boiling water bath, you can still use your pressure canner for that. The reverse is not true- this kind of canner only does one thing. If you decide down the road that you want to preserve meats or low acid vegetables, you're still going to have to get a pressure canner.
On a side note, pressure canners and pressure cookers are not necessarily the same thing. You can use a pressure canner for pressure cooking, but you can't use a pressure cooker for canning. Your best investment is a good pressure canner, they do just about everything.