[Master Shake]

I am pretty sure that the income displayed is gross, and is for the next turn, not the current one. So the thing to do would be to look at:

gross income - upkeep

and add that to your left over cash at the beginning of the turn. One thing that is unclear, is wheter you have to pay upkeep on units the turn your recruit them. In other words, you might miss out a few gold because the upkeep does not include new units you are recruiting.