To fund your excessive military budget, various options are laid out for you. Take over enemy controlled banks, drill for oil, or take enemies hostage/release prisoners from enemy camps. If done correctly, you can be left with an almost limitless supply of money. When taking enemies as prisoners, you can either "interrogate" them to reveal sections of the map, or you can just detain them and have them generate more income. Beware, though, injured soldiers on your own side that aren't rescued can also become hostages.
There's really little to say about Act of War. It's a great game that does everything right, though nothing original. Unfortunately, it will probably get lost in the shuffle and be played by few. The multiplayer is worth playing by itself for any RTS fan (It's exactly like every other online RTS, with the US Army, Task Force Talon, and the Consortium offering 3 differentr building and unit trees), and the action packed, story driven campaign is icing on the cake. Anyone with an interest in the genre owes it to themselves to pick this gem up.