Where did the knights of the order receive food and funds for building castles and replenishing equipment?

There were several sources of income:

1) Booty in wars;
2) Taxes of peasants.

Every large feudal lord in the Middle Ages had land where peasants worked. For this reason, they were forced to pay tax for the use of land. The proceeds from taxes were used to build fortresses and to maintain the troops. Of course, there were often cases when feudal lords fought with each other and could receive rich booty during the war. The feudal lords were guided by the same goal when they went to war in the Holy Land.