Hm. This topic is posted in
IO - Classic and Version 4 Realms, but thought it should be in Age of Conquest board.
The villagers are happy enough I think, and I think if you hired some army that is outside, the gold, should go negative.
So how samy said, raise your taxes a little and your gold should slowly turn into positive number.
Ofcourse, if your taxes won't be enough high, your gold should go to more (-).
Always look if you can handle high taxes: press on the green smiley, there you can see who adds you happines and who minuses the happiness.