i think there should be a money idea for a market at spawn and you could have to pay for commands. You should be able to sell stuff too to get the money

We used to have NPC merchants and a banking system on our old server, but I think most of them were removed due to the plugins being too much work to keep up to date or something like that.

Can't shop-style trading now be done with redstone and comparators anyway? I seem to remember seeing some videos on shops and monetary systems. Not that I could build that, but someone with more time and more inclination might be able to make something awesome! I'd contribute any resources needed; I have chests full of redstone, iron, quartz and other sundry items.

You are correct, its something i plan to do, just GTA V happened and i find myself hooked on that at present.