This is typical Berlin: a unique, hidden place in a street where there's literally nothing. A fresh alternative to flea markets or typical second-hand clothes shops such as Humana, Schöneberg's Garage provides second-hand clothes that can be bought at a fixed price per kilo.
As an example my girlfriend bought a hat, a leather jacket and a vest for less than 20 EUR. Carefully cleaned afterwards, of course .
Tip: These are the coordinates. You can reach this by Nollendorfplatz U-Bahn.