Landownership
The most important source of income for nobles was landownership. Many noble families owned large estates in the countryside, which provided them with a steady income from rent and agricultural production. They typically employed peasants to work the land and paid them a share of the harvest. In addition, some nobles also owned urban properties, such as houses and shops, which they rented out to merchants and artisans.
Trade
Many noble families also engaged in trade, both locally and internationally. They might export agricultural products, such as olive oil, wine, and wheat, to other parts of Europe and the Mediterranean region. They might also import luxury goods, such as spices, silks, and jewelry, to sell to the local market.
Military Service
In times of war, nobles often served as military leaders and commanded the city-state's armies. They were expected to provide their own weapons and armor and to lead their troops into battle. In return, they were rewarded with land, wealth, and political power.
In addition to these three main sources of income, some nobles also held government offices or were involved in other professions, such as banking and medicine.