Go to Upgrade Settings:
Choose your desire upgrade on left box. Then uncheck the 'Use Defaults for (Upgrade)'. Go to 'Gas Cost' and change the value to 0 in the 'Base' and 'Factor' box.(Base is starting upgrade and Factor is how much it goes up by on each upgrade).
To get the 'Time Cost' factor to be 0, or instant, put in the value 8739:
