Trade, and kill bandits while you trade.
Without a fief it is harder, because there is no place to leave your men. Consider cutting down you party to 30 - 40 men. Morale stays high and you move fast on the map (which is another advantage in trading, you get faster from place to place and it is less boring).
I am currently making about 10,000 denars a week as king with a city plus villages that are costing me about -2,500 to - 3,500 per week. 35 people in my party. I always take out some recruits with some top tier troops and train them up (or get them killed) during the one-week trips.
My top trade routes are wine from Suno to anywhere, but preferably Ahmerrad, iron from Curaw to anywhere, but preferably to Reyvadin or Khudan, spice and salt from Tulga (I think) to anywhere, flax bundle, wool, linen from Sargoth to anywhere.
Cheers,
T.