Answer by taking a quote from the following article:

Abu al-'Ala` al-Ma'arri (Arabic 'bw l`l lm`ry Abu al-'Ala` al-Ma'arri, full name 'bw l`l 'Hmd bn `bd llh bn slymn ltnwkhy lm`ry Abu al-'Ala` Ahmad ibn 'Abd Allah ibn Sulaiman al-Tanuhi al-Ma'arri; December 973 - May 1057) was a blind Arab philosopher, poet, and writer. Al-Ma'arri held and expressed an irreligious world view which was met with controversy, but in spite of it, he is regarded as one of the greatest classical Arabic poets.

Abu al-'Ala` was born in Ma'arra, modern Maarrat al-Nu'man, Syria, near the city of Aleppo, in December 973. At his time, the city was part of the Abbasid Caliphate, the third Islamic caliphate, and was during the Golden Age of Islam. He was a member of the Banu Sulayman, a notable family of Ma'arra, belonging to the larger Tanukh tribe. One of his ancestors was probably the first qadi of Ma'arra. The Tanukh tribe had formed part of the aristocracy in Syria for hundreds of years and some members of the Banu Sulayman had also been noted as good poets.  He lost his eyesight at the age of four due to smallpox. His later pessimism may be explained by his virtual blindness. Later in his life, he regarded himself as "a double prisoner" which referred to both this blindness and the general isolation that he felt during his life.  He started his career as a poet at an early age, at about 11 or 12 years old. He was educated at first in Ma'arra and Aleppo, later also in Antioch and other Syrian cities. Among his teachers in Aleppo were companions from the circle of Ibn Khalawayh. This grammarian and Islamic scholar had died in 980 CE when al-Ma'arri was still a child. Al-Ma'arri nevertheless laments the loss of Ibn Khalawayh in strong terms in a poem of his Risalat al-ghufran. Al-Qifti reports that when on his way to Tripoli, al-Ma'arri visited a Christian monastery near Latakia where he listened to debates about Hellenistic philosophy, which planted in him the seeds of his later scepticism and irreligiosity; but other historians such as Ibn al-Adim deny that he had been exposed to any theology other than Islamic doctrine.  In 1004-5 al-Ma'arri learned that his father had died and, in reaction, wrote an elegy where he praised his father. Years later he would travel to Baghdad where he became well received in the literary salons of the time, though he was a controversial figure. After the eighteen months in Baghdad, al-Ma'arri returned home for unknown reasons. He may have returned because his mother was ill, or he may have run out of money in Baghdad, as he refused to sell his works. He returned to his native town of Ma'arra in about 1010 and learned that his mother had died before his arrival.  He remained in Ma'arra for the rest of his life, where he opted for an ascetic lifestyle, refusing to sell his poems, living in seclusion and observing a strict vegetarian diet. His personal confinement to his house was only broken one time when violence had struck his town. Though he was confined, he lived out his later years continuing his work and collaborating with others. He enjoyed great respect and attracted many students locally, as well as actively holding correspondence with scholars abroad. Despite his intentions of living a secluded lifestyle, in his seventies, he became rich and was the most revered person in his area. Al-Ma'arri never married and died in May 1057 in his home town.

How old was he?
He started his career as a poet at an early age, at about 11 or 12 years old.