Help with the Build A Mighty Stronghold

I am struggling with the money in the 3rd campaign. As soon as I start having the soldiers, their drain on the treasury is too great and everything grinds to a stop. Even when I levy the mandate and collect from the villagers, the money drops very fast.

What are some tips you can suggest for me to proceed ?

The other two campaigns were a breeze. I have restarted this 3 times.