Where did Athens get money to rebuild after the Persian War?

Answer 1

It continued to extort the war contributions from the Delian League cities after the war ehded. This money it spent on maintaining its fleet to take the money, and spent it on glorifying the city, supporting its culture and lifestyle, and keeping half its own population on the public payroll.

The gold enabled a Golden Age.

Answer 2

The city was not destroyed during the Persian invasion and occupation as the Persians used its accommodation as a base. They did however destroy the temples and gods as payback for the destruction of the statues and temples by Athenian soldiers in the Persian provincial capital of Sardis two decades earlier when Athens sent a force to Asia Minor to help a revolution by the cities of Ionia.

When the Persians left Athens in 479 BCE, the Athenians rebuilt the city walls and also built two walls providing a protected connection to the city's port. The work was done by its citizens and slaves using whatever materials they could lay hands on, so it cost time and effort, not money.

Athens got money later on from getting paid by other city-states so their navy could protect them from the ongoing Persian threat. After the Persian threat receded they diverted the money for their own public works (Parthenon etc) a fleet to dominate the other cities and keep half their population on the public payroll.