What is the ruling on not informing parents, relatives, and neighbors of one's true salary, especially parents and relatives, and how can one use equivocation in such a situation?

There is no blame in not informing your family of your true salary. It is appropriate to use dissimulation (tawriya) and indirect speech (ta‘ridh), because lying is fundamentally impermissible, and in dissimulations there is room to avoid it.