I've been using cast iron cookware for years and several of the pieces belonged to my great grandmother. We're still using them. Old cast iron is quite collectable and some of the skillets are worth over a $100 and I have a cornbread pan that will cost you $250 if you can find one.
If you are searching garage sales look for Griswald first, then Wagner, next lodge and most unmarked aren't worth buying. One of the things that makes the old skillets so good is that the surface is worn smooth. I've found you can take a minigrinder with a knotted wire wheel and quickly smooth the surface. Then you season them and after a few seasoning they are good to go. One problem with iron skillets is that the exterior tends to build up a scale. When this start to become an issue just stick them in the oven and turn of the self clean cycle. It does a beautiful job of cleaning them. Then just wash them, reseason and you're back in business.
If you are searching garage sales look for Griswald first, then Wagner, next lodge and most unmarked aren't worth buying. One of the things that makes the old skillets so good is that the surface is worn smooth. I've found you can take a minigrinder with a knotted wire wheel and quickly smooth the surface. Then you season them and after a few seasoning they are good to go. One problem with iron skillets is that the exterior tends to build up a scale. When this start to become an issue just stick them in the oven and turn of the self clean cycle. It does a beautiful job of cleaning them. Then just wash them, reseason and you're back in business.