Still, if you have to have the cash, it can be a lifesaver. Each side has fairly different units. The units of the Imperium tend to be hover vehicles and brute force killing machines. The Freedom Guard has higher technology units of a wider variety. Each side therefore requires differing strategies.
Many structures require another structure to be built or upgraded before they can be built.
Units can only be built by the appropriate structures. Also familiar is the progressive nature of how the campaign missions introduce units and structures. As you play through the missions more and more structures and units become available each mission until towards the end you can employ the full gamut of forces. You select one or more units and then issue the attack command by clicking on an enemy unit or structure. You can also force units to attack while stationary if need be.