Is it permissible for a husband to prevent his wife from working, given her need for money and her desire for it, and her refusal to complete her studies?

As long as you have not consummated the marriage with your wife, she is not obligated to obey you regarding her refraining from going out for work or study. However, after consummation, you have the right to prevent her from going out, unless she stipulated in the marriage contract that she can go out for work, in which case her condition is binding. If there was no such condition, but you merely promised her permission to work, this promise is not binding, and there is no sin upon you for retracting it for the sake of benefit, for the Prophet, peace and blessings be upon him, said: "And by Allah, if Allah wills, I do not take an oath and then see something else as better than it, but that I expiate for my oath and do that which is better, or I do that which is better and expiate for my oath."