Canning does not take much expense. The biggest expense is the jars. The pot and book and other utensils are not that expensive.
And once you own them, they are yours forever.
A pressure canner, however, is a different matter but I use mine a lot so it’s been worth it. You absolutely have to pressure can veggies and meats. Fruits can be hot water bath canned. I have lots of cans of turkey soup from Thanksgiving dinners canned up.
When the shtf, tomatoes can be water bath canned in a solar oven. “Solar canning is safe for acid foods only. Acid foods are fruits and tomatoes, or their juice, jams, jellies. DO NOT CAN MEATS OR VEGETABLES IN YOUR SOLAR COOKER!!! Don’t even add a sprig of parsley as botulism can grow on any non-acid food!” http://solarcooking.wikia.com/wiki/Solar_canning
Build your own solar oven with simple items around the house such as foil covered cardboard. http://solarcooking.org/plans/
Pressure canners can be found at yard sales and thrift store or ask around. I have two yard sale bought big ones and one small inherited pressure canners. Have them tested at the home extension office. FYI, new gaskets can be hard to find. Replacement gaskets made in Japan may not fit properly so do a search for comments about your model.