Should I donate a quarter of my monthly salary ($500), or keep most of it for my future and my mother's future, given my difficult circumstances and my need for my own housing?

If the vow is not uttered, then nothing is incumbent upon it, because it is not formed by mere intention, as the Prophet, peace and blessings be upon him, said: "Indeed, Allah has forgiven my nation for what crosses their minds, as long as they do not act upon it or speak of it." However, if it is uttered, then fulfilling it is recommended but not obligatory; it is among the noble virtues.