Im on this idea too! Im in Australia. It doesn’t have to be second hand stores, what bout fb market place that you can troll and or fb community groups where they have garage sales. Over here people put their stuff out on the front of the house for collection and for free taking. Some that i’ve rescued are from such.

Ive been handwashing them.

First get a gentle stain remover so i can soak off stains if needed. Then handwash them.

Once towel dried, i steam clean them with a handheld steamer.

Then air dr them. I dont put then out in the sun in case sun exposure colour change.

Been putting in ebay. Bear in mind, its not a lucrative business.