It's true! Many jars of food or ingredients that you already need in the kitchen can be used for canning purposes, and there are some really fancy like those of some brands of marmalade.
I usually do the same as Sat, wash thoroughly the jars, which ca be sterilized either with a machine or into boiling water. Otherwise I may go to a supplier store when I need specific containers for a given canning project. Usually canned food to give away in this last case.