He doesn't need an official building for that to happen, he could just set aside a field and let people set up their own stands - those kinds of free markets are very enjoyable, maybe throw the occasional festival (that's the medieval way, and unlike the parties children get to have fun as well. For families that is a big load off of their backs). But with less than a thousand people around there isn't that many potential buyers, especially not when Richter provides most stuff free of charge. Once mama arrives with her caravan, the market could work. Hopefully she will do away with Richter's current economic "system" or at least force Richter to let capitalism have a place.