You kill a monster you get silver. 40 max. if your commanding lord for that faction set it to 0 then no you dont get silver.
Buying regs from vendors doesnt put silver into the city. There just there for peoples convienence (however you spell that). Everyone thinks they support the factions with silver in turn they drain them from it by placeing them, 500 silver a day from the ore, lumber, bottles, reg vendors. The horse breeders are more and the Guards cirtianlly are more.