In order to get this acvhievement, the player has to make 10 deals in Metro 2033 and 30 deals in Metro 2033 Redux. Purchasing or selling weapons or equipment (e.g., filters, grenades and medkits) counts towards this achievement, while trading ammunition does not count.
The player can obtain this achievement at any time during the missions Exhibition and Polis, since there are no more vendors after the aforementioned stations. In the Redux version, trades from Metro 2033 are combined with trades from Metro: Last Light. However, it is not difficult to get it by playing Metro 2033 alone.