Because my spouse has been heavily involved in the development of a thrift store for a state-wide immigration and refugee services organization, I have had a lot of time to think about and explore the dimensions of thrift stores in all their glory.
One big conclusion: like all nonprofit revenue generating ventures, it's not simple to organize. There are many details and a good business plan that maps out these details: who does what when and particularly, where is the best location, how are customers recruited, and how many sales are really needed to at least cover costs? Having a key person seeing to all these details is also critical. And, having some cash to make it all happen, even with volunteer organizers, is essential.
Thrift stores are an age-old revenue-generator for nonprofits. The pioneers like Goodwill and the Salvation Army have illustrated how it can be done. And the big new kid on the block, Savers, has really offered another model that particularly benefits nonprofits that couldn't really manage a store on their own (the majority of nonprofits I might add).
All that said, there is another side to thrift stores and particularly, the donated inventory which is really the most essential ingredient. I thought this Slate Magazine article and some of the linked articles pretty thoughtful for those donating to, shopping at, and, or, operating or thinking of operating a store.