[ConservativeStatement]

In your opinion, where do people who own and operate secondhand stores get their merchandise? Exclusively from individuals looking to sell items or do they go to these storage sales and hope to find items for future sale?

[sima_yi]

...where do people who own and operate secondhand stores get their merchandise?

Based on just my own experience, I think most of the secondhand store stuff is donated. The very few times I found anything in an abandoned storage unit that was worth anything, the (facility) owner would donate it to Habitat for Humanity.