Is it reasonable to assert that Muhammad, upon him be peace, might have claimed prophethood to attain some material gains? This question may be answered by looking into his financial status before and after prophethood. Before his mission as a prophet, Muhammad, upon whom be peace, had no financial worries. His loving and rich wife, Khadijah, may Allah be pleased with her, had made available to him all that he needed. As a successful and reputed merchant, Muhammad had a comfortable income. It is ironic that the same man, after his mission as a prophet and because of it, becomes worse off materially.
Describing their life, his wife, Aishah, may Allah be pleased with her, narrated that a month or two might have elapsed before fire was lit in the Prophet's house (to cook a meal), while the household subsisted on milk and dates. (Riyad al-Saliheen) After eighteen years of his mission, when Muslims emerged victorious, we still find a kind of revolt in Muhammad's household in protest to the difficult life characterized by a considerable self-imposed material deprivation. This incident took place at the time when the Muslim treasury was under his disposal (Bukhari, Muslim). Asked about Muhammad's bedding Hafsah, may Allah be pleased with her, answered, "It comprised of a piece of canvas which I spread double folded under him." Bilal, may Allah be pleased with him, reported that the Prophet never kept back anything for future use, tha t he spent what he had on the poor and needy, and that on one occasion, Muhammad received a gift of four loaded camels, yet he took nothing for himself and he further insisted that he would not go home until the whole lot was given away to the needy. (Riyad al-Saliheen) At the time of his death, and in spite of all his victories and achievements, Muhammad, upon whom be peace, was in debt, and his shield was in the hands of a Jewish citizen of Madinah as a collateral for that debt! (Riyad al-Saliheen)
One may then inquire: Are there any materialistic motives behind Muhammad's claim of Prophethood?
Islam: A Way of Life and a Movement, "Muhammad's Prophethood: An Analytical View" - Jamal Badawi, pp. 69, 70