First you have to be Soviet, Build all the way to a battle lab and build that to.
Now build Cloning Vats and wall off the barracks all around tightly against the side.
Now you get free men*. Next build as many men as you want (since they are free) and send them back into the Cloning Vats*. There , Free Money!
*#1: You have to have enough money to buy it, and then you get your money back, and a clone comes out of the Vats!
*#2: Except For: Crazy Ivan, Crono Ivan, Chrono Commando, Engineer, rocketeer, Tanya And Yuri Prime.
NOTE:Any unit that teleports takes several tries to go in, so continuely press the button.