Buffalo Exchange is like a indoor yard sale ran by über-hipster university kids... Only the merchandise is a little less beat down then what you would find at a yard sale and I am pretty sure they take plastic.
I have never tried to sell items at this location... Back when I lived in Tucson, Arizona and was trendier I would try to sell items to the local BE and was always disappointed with what they were willing to take, and the credit they would give me for it. So I just donate my used clothing now... If you do plan on selling, just remember, they are only going to buy things they know will sell. So if you no longer want an item because it's out of style, faded, whatever.... chances are they won't either!
Shopping here can be a bit hit or miss... Make sure you allow yourself ample time to browse. Sometimes I will find absolutely nothing that catches me eye let alone warrants a try on... Other times I find amazing deals on great brand name, slightly worn items. Like gorgeous leopard print pumps for $20 that I have seen in the mall for $120.
A tip: When you check out, you will be asked if you want a bag or a token. If you take the token, you can then select a box for one of three charities to put your token in... And then Buffalo Exchange donates to that charity. :)