What is the ruling on a woman traveling to earn money in the absence of a mahram?

The basic principle is that it is impermissible for a woman to travel without a mahram (definition), due to the Prophet’s (peace and blessings be upon him) saying: "No woman should travel except with a mahram." If there is no pressing need for travel, then it is safer to avoid it. However, if she is compelled by the need for money or in dire need of it—a need that approaches necessity—then there is no harm upon her, because "necessities permit the forbidden." In such a case, she must exercise extra caution in covering herself, observing hijab (definition), and avoiding anything that might cause fitna.