This can be translated in active form. Alternate translation: "if they build the city and complete the wall" (See: [[rc://en/ta/man/jit/figs-activepassive]])
This is probably a merism for "any kind of taxes." (See: [[rc://en/ta/man/jit/figs-merism]])
# taxes
This word probably refers specifically to taxes on goods that people bought or consumed.
# tolls
taxes that people needed to pay to use roads
# and that will harm the treasury of the kings
They will "harm the treasury" by not giving money to the kings. Possible meanings are that the writers of the letter use the word "kings" 1) to refer to Artaxerxes and his descendants or 2) to honor Artaxerxes by referring to him in third person plural. (See: [[rc://en/ta/man/jit/figs-123person]])