"做旧货生意的" can be translated into English as "a second-hand goods dealer" or "someone in the second-hand goods business".
For a more concise and colloquial expression, you could also say "a used goods seller" or simply "a second-hand dealer".
Here are a few examples in context:
He is a second-hand goods dealer, specializing in antiques and vintage items. (他是一名做旧货生意的,专门经营古董和复古物品。)
She makes a living by being a used goods seller in the local market. (她靠做旧货生意在当地市场谋生。)