There are many ways to generate money. See here:
Money Manking American Night Club - Cncmaps Map Editing Forums
For a map.ini mod and single player map in which America can build the Night Club. You send your GIs there on RnR and they will spend loads of cash there which you can then pump back into the war effort. They also gain experience and become bigger and bigger spenders the more time they spend in there, so it is a good way to train up hordes of veteran infantry.
Basically the night club behaves like an internet center and the infantry get the HackerAIupdate.
Note that if you select the building and press S to stop (like if you want them to stop shooting at something), the infantry inside will stop spending money, so you have to exit them and garrison them in it again to restart their spending.
Another way which will get you money fast is to be able to spawn new supplies for your harvesters (workers, chinooks, supply trucks) to collect. I am working on a mod in which there is one such building, which can be built by the China Nuke General. The build tech tree is War Factory > Uranium mine > Uranium Ore Enrichment Factory.
You can download a preview version of the mod here:
Beng's Demo General Mod - Cncmaps Map Editing Forums
On the dozer you need to press the switch command sets button (like on the GLA worker) to get the buttons for the new buildings as there were not enough slots on the command set for them.
The Ore enrichment factory makes enriched uranium that is then barter traded on the global black market in exchange for supplies. Play generals challegne or skirmish as Nuke, and tech up in that order to see the building.
In coding terms, the Ore enrichment factory object has an OCLSpecialPower module that is triggered by an object level upgrade. This upgrade is in turn removed by another upgrade so that it can be bought again and again (see the method used by the GLA worker to switch between command sets).
The OCL spawns a temporary object which has a GenerateMineField behavior (see the cluster mines bomb for an example of how this works with objects that generate minefields when they die). The minefield is not made of mines but of supply piles.
Oh, and as for the uranium mine in that mod, the miners inside are able to dig through the earth from China and emerge on the other side of the earth, thus enableing your units to pop out somewhere else (ie it is a tunnel network with built-in sneak attack power).
The mod includes my laser general mod and Demo general mods. It is not finished yet and there are a few bugs i need to fix, like the nuke general's minigunners acidentally affecting themselves with the negative frenzy bullets that make them have less range and slower firing.