I've been doing this all my life, and I can give some good tips:
I inherited an old, old canner from an elderly family member, so my cost was zero. You might find one used. Be aware that three types of canners exist:
- Hot water bath; this is nothing but an extra-large pot (with a piece on the bottom to keep the jars from touching the actual bottom of the pot /to allow water under the jar), and it is the simplest type of canner. It can only can acidic fruits and vegetables, but that covers a wide range: tomatoes, green beans, peaches. It's also good for relishes and salsas, which contain only acidic foods. Hot water canners can be had -- new -- for $30 or so at Walmart. This type of canner is your obvious first step; you don't have to mess with the pressure.
- Pressure cooker canner; this type can can meats and non-acidic vegetables. It is more complicated, and the foods must "stay in" longer periods of time. These are more expensive. I'm going to guess $100+ You can hot-water-bath can in a pressure cooker, but you cannot pressure cook in a hot water bath; thus, this is a more versitile item.
- Steam canner; though the official sources say that this isn't an acceptable way to preserve food, my family's been doing it forever, and none of us have been injured. the benefit is that it's not so heavy and can be used on glass-top stoves.
All these canners come in a variety of sizes. The larger ones are attractive, of course, because you can preserve more jars in one "round" of cooking, but the smaller ones don't weigh nearly as much.
Which brings me to a warning: If you use a heavy canner on a glass-top stove, you may be buying a new stove. No amount of canned green beans can make up for that cost, so be careful. An acceptable option: Buy an "electric eye" and use it on the counter top. I'm very interested in buying an electric canner, which plugs into the wall and doesn't use the stove at all. My main motivation is that I could prepare my foods in the house, then let the canner run outside on the back porch, keeping all that heat outside. I am holding out, however, because they cost about $300, and that's tough to justify. If I could find one used for half the price, I'd snap it up. Also, the electric models are ONLY hot water baths.
Next you need jars. These aren't so difficult to find. Check out old antique stores. In my experience, they run .25 to .50 each, and they're likely to last you the rest of your life. Avoid the type with the wire bail that flips over the lid -- it's near impossible to get the rubber rings necessary to close them. The pretty blue ones are rare; thus, they're expensive. I like pints better than quarts. They fit my family size; however, I do like to have some quarts for things like spaghetti sauce. Wide-mouth rings will cost more, but wide-mouth jars are nice for packing pickles. The experts say you shouldn't re-use commercial mayonaise or spaghetti sauce jars, but my family's been doing it forever without trouble. IF the food doesn't process properly, you'll see that the jar isn't sealed, and you can run it through again (or just eat the food immediately).
In addition to the canner and jars, you'll need some accessories: Lids and rings and a wide-mouth funnel are all that really matters. You already own long-handled spoons. A magnetic lid-lifter is handy for lifting lids out of the not-quite-boiling water. A lift-out thing that keeps your lids separated while they're submerged in boiling water is also nice, but I don't have one myself.
Finally, you're going to need some food to process. Commercially canned food is pretty cheap when purchased on sale, so to make this a money-saving enterprise you really need to grow the food yourself OR get it very cheaply. At the end of the season I can almost always get a bushel of apples or a large box of tomatoes for $10. These are often labeled "canning quality", which means they have bad spots that must be cut out.
Regardless, I rarely save money on canned food; rather, I can have better quality for the same price as store-brand sales (my thick, tasty homemade applesauce bears no resemblance to that watery stuff they sell at the store) . . . or I can have unusual items, like my great-aunt's pepper relish (why would you ever eat meatloaf without it?), for the same price as store-bought stuff . . . or I can have things that can't be purchased commercially like Stawberry-lemonade concentrate.
Two last suggestions:
Check out several canning books from the library. The instructions are simple to follow. Or look online -- you can find plenty of canning websites. Do not modify the recipes. Think of this as chemistry class rather than a creative endeavour.
Consider taking a class at your county's Home Extension office. They're typically offered in the summer, and that type of class tends to run $10 or less.