Items such as anvils, old tools, pots and pans, and encampment pieces can sometimes be found. We're talking about Goodwill, Salvation Army, etc. These places generally offer great bargains. Shop these places often as their inventory changes frequently. For the prices charged at these sales, they're well worth the time and effort to shop them.
People sell used items at much lower than new prices.
Items include everything from camping gear to fabric. Check the listings, especially on weekends. Usually there are several pages of paid advertisements which offer re-enactment type wares by various members and businesses. You may already own some items which are perfectly suited for SCA use. Often you can borrow needed items from someone in your group.