I know that most diocesean priests don’t take a vow of poverty. But what about the pope?
No, the pope does not take a vow of poverty. However, in 2001, the Vatican revealed that the pope also does not receive a salary (source). The Vatican budgets provide for the pope’s material needs and he does not receive a salary on top of that. In John Paul II’s will, he revealed that, with the exception of personal papers and odds and ends, he did not leave behind any personal property of which it was necessary to dispose.
All the Pope’s Men by John L. Allen Jr.