There is roughly 300,000 people in the entire country, 0.5% of which are ninja, who almost all resided in Leaf.
The city of Konoha suffered an eight percent damage as a result of the Kyuubi's rampage. Correspondingly, the damage caused trade to plummet for three months straight and the economy of Fire did not recover until three years later after the rampage.
Fire country is presumably primarily an agricultural society. The soil of Fire country is extremely rich, and would bring massive increase in GDP if it could be cultivated.
Taxation is high and farmers are usually poor.
The wealthiest are the ninja clans, likely followed by either landowning nobles or merchants.