Cargo Hold

Every ship should be able to carry at least a little cargo even if it is just for the ships personal supplies.  Of course this is take up the majority of space in a freighter.  A typical tramp freighter will have between 5 and 20 cargo units while some of the mega-freighters will have hundreds.

1 Cargo unit:  Cost: N/A (it's just empty space after all and will be accounted for in the cost of the hull),
Mass: 0, volume 150 cu m.