Although there can be many problems causing a squeaky vehicle, the most-common cause is a bad fan belt. A replacement belt can be bought for approximately $10, and it can be installed quickly at an auto shop or easily installed at home using a ratchet.
If the squeaking noise still persists after a new fan belt is installed, check the power steering fluid in the vehicle, as low fluids are another common cause of a squeaky vehicle. Worn brake pads are another common culprit. If none of these are the cause, it's best to have an experienced mechanic diagnose the problem.