In order to be a charity, one important thing is to be a not-for-profit organisation. That doesn’t mean that organisation cannot acquire assets (like buildings) to carry on its activities. It means that no one can take any profits from the organisation as an investor or share-holder. So, presumably, no one gets any dividends paid out of Goodwill: it all gets reinvested in the business. In addition, if it ever would up as a business, there would have to be rules that anything left over after winding up would have to be given to other non-profits carrying on a similar business.
And presumably, the way that Goodwill keeps from making a profit is by adjusting the prices they charge for the merchandise. When you buy something at a thrift shop, your money isn’t enabling them to buy more merchandise (since they get it donated for free), but it is going to pay for the salaries of their employees, paying the electric bill for the store, and supporting whatever other charitable enterprises they have going. If they find that they’re getting more money in from sales than they can spend on such things, then they just lower prices.
Um, no, they simply increase their charitable actions. More money from sales of clothing equates to more money available to obtain and provide charitable services to the poor, etc.
Essentially all that makes you a non-profit is that you don’t intend to make money for “profit,” that is, for the purpose of lining the pockets of the owners with money. It doesn’t restrict you from making money that you use for other legitimate purposes of your business.
Depends on the charity, probably. And making clothes and other necessities available to the poor at low price is itself a charitable action, so making them available at even lower price would be one way to increast their charitable actions.