As Grand Vizier, he collected vast wealth.
Even Rüstem's sworn opponents admitted, that he never boasted of his wealth or power (although he was a man of fortune), and that he was the very first Grand Vizier in the history of the Ottoman Empire who significantly contributed to the development of the state from his own funds.
According to most period testimonies (excluding Taşlıcalı Yahya Bey's "Şehzade Mustafa Mersiyesi"), Rüstem was considered one of the few state dignitaries who didn't take bribes.
Nonetheless, Rüstem's famous economic talent and his modest way of life, both highly valued by the Sultan, made him rich, even before his marriage to Mihrimah Sultan.
In his last will (a part of endowment charter from 1561), Rüstem made an inventory of every single detail of his property, in order to secure his great foundation projects after his death.
Rüstem's testament determines exactly which part of his property belongs to the state, to his foundations, to the Hurrem Sultan's foundation and to Mihrimah's foundations, what he leaves to his wife Mihrimah and to their daughter Ayşe Hümaşah Sultan.
He determines his wife Mihrimah Sultan as executor of his last will and his daughter Ayşe Hümaşah as the executor and administrator of his foundations.

All historians emphasize Rüstem's relentless hard work to consolidate the troubled economy of the Ottoman Empire - impoverished by excessive spending on wars and a lavish lifestyle of the court - and his efforts to improve it.
The period documents say that he also generously financed this upswing from his own resources.
On his lands were built toll free bridges, roads, covered bazaars, granaries, baths, hospices, caravanserais, convents, schools and various other establishments for the public benefit.
Their funding was largely secured by the leasing of Rüstem's estates.
He supported agriculture, founded new trading centers, like the bazaar in Sarajevo or silk factories in Bursa and Istanbul, social and educational institutions.
He developed the domestic economy by encouraging major public works projects and built a modern infrastructure: trade routes, and water networks in Istanbul, Mecca and Jerusalem.

He also found enough money in the treasury to make Suleiman's dream come true (Süleymaniye Mosque, 1550–57), as well as to fund other monumental architectural projects realized by the legendary Mimar Sinan.
To reduce protectionism in the state administration, an official installment fee was introduced, and confiscated when the officials misused his authority.
Rüstem's reform of the military remained unfinished.
At the time of his death in Constantinople on 10 July 1561, his personal property included 815 lands in Rumelia and Anatolia, 476 mills, 1700 slaves, 2,900 war horses, 1,106 camels, 800 gold ambroidery Holy Qur'ans, 500 books, 5000 Caftan, 130 kinds of armors, 860 gold embroidered swords, 1500 silver tolga, 1000 silver balls, 33 precious jewels etc.

The Rüstem Pasha Mosque (Turkish: Rüstem Paşa Camii) is an Ottoman mosque located in Hasırcılar Çarşısı (Strawmat Weavers Market) in Fatih, Turkey, which was designed by Ottoman imperial architect Mimar Sinan for Grand Vizier Rüstem Pasha.
It was built between 1561 and 1563.
As Grand Vizier, he collected vast wealth. Even Rüstem's sworn opponents admitted, that he never boasted of his wealth or power (although he was a man of fortune), and that he was the very first Grand Vizier in the history of the Ottoman Empire who significantly contributed to the development of the state from his own funds. According to most period testimonies (excluding Taşlıcalı Yahya Bey's "Şehzade Mustafa Mersiyesi"), Rüstem was considered one of the few state dignitaries who didn't take bribes. Nonetheless, Rüstem's famous economic talent and his modest way of life, both highly valued by the Sultan, made him rich, even before his marriage to Mihrimah Sultan. In his last will (a part of endowment charter from 1561), Rüstem made an inventory of every single detail of his property, in order to secure his great foundation projects after his death. Rüstem's testament determines exactly which part of his property belongs to the state, to his foundations, to the Hurrem Sultan's foundation and to Mihrimah's foundations, what he leaves to his wife Mihrimah and to their daughter Ayşe Hümaşah Sultan. He determines his wife Mihrimah Sultan as executor of his last will and his daughter Ayşe Hümaşah as the executor and administrator of his foundations.
All historians emphasize Rüstem's relentless hard work to consolidate the troubled economy of the Ottoman Empire - impoverished by excessive spending on wars and a lavish lifestyle of the court - and his efforts to improve it. The period documents say that he also generously financed this upswing from his own resources. On his lands were built toll free bridges, roads, covered bazaars, granaries, baths, hospices, caravanserais, convents, schools and various other establishments for the public benefit. Their funding was largely secured by the leasing of Rüstem's estates. He supported agriculture, founded new trading centers, like the bazaar in Sarajevo or silk factories in Bursa and Istanbul, social and educational institutions. He developed the domestic economy by encouraging major public works projects and built a modern infrastructure: trade routes, and water networks in Istanbul, Mecca and Jerusalem.
He also found enough money in the treasury to make Suleiman's dream come true (Süleymaniye Mosque, 1550–57), as well as to fund other monumental architectural projects realized by the legendary Mimar Sinan. To reduce protectionism in the state administration, an official installment fee was introduced, and confiscated when the officials misused his authority. Rüstem's reform of the military remained unfinished. At the time of his death in Constantinople on 10 July 1561, his personal property included 815 lands in Rumelia and Anatolia, 476 mills, 1700 slaves, 2,900 war horses, 1,106 camels, 800 gold ambroidery Holy Qur'ans, 500 books, 5000 Caftan, 130 kinds of armors, 860 gold embroidered swords, 1500 silver tolga, 1000 silver balls, 33 precious jewels etc.
The Rüstem Pasha Mosque (Turkish: Rüstem Paşa Camii) is an Ottoman mosque located in Hasırcılar Çarşısı (Strawmat Weavers Market) in Fatih, Turkey, which was designed by Ottoman imperial architect Mimar Sinan for Grand Vizier Rüstem Pasha. It was built between 1561 and 1563.
Rüstem Pasha