His father and uncle were merchants, so when his mother died, his uncle (Abu Talib) took the orphan in, training Muhammad to become a merchant.
As I understand it, his first wife, Khadija, was a widow and a successful merchant. She was also related to the younger Muhammad, when she employed or hired him, before they married.
The detail of Muhammad about his life before becoming a prophet (in 610), are at not very reliable, because they are often distorted and embellished, as they are when he became during his prophethood (610 - 632). The Qur'an doesn't provide much in detail about Muhammad's own life, and I would hardly call the Qur'an, a "history" book.
According to these biographies he was a very astute and wise merchant, said to be known for his trustworthiness. But like I have said, these biographies and history about Muhammad (both before and after becoming a prophet) are not reliable, and the earliest biography was over a century after Muhammad's death, in the 8th and 9th centuries.