Is it permissible for the sister of the questioner, whose husband has passed away and who has a minor son, to enter into an 'urfi marriage (customary marriage) or a misyar marriage (traveler's marriage), provided that the conditions for marriage are met, in order to preserve her livelihood, her administrative housing, and the interests of her children, and what is the legitimate and legal formula for such contracts?

The marriage is valid if it meets the conditions of a legitimate marriage, and its non-declaration does not affect it. It is permissible for the wife to waive some of her rights. Publicizing the marriage is preferable to avoid suspicion. There is no special formula for such a marriage; offer (ijab) and acceptance (qabul) are required. It is recommended to document the contract to preserve rights. The son undertakes the marriage contract of his mother in the absence of the father or grandfather. The considered compatibility is in religion and character. It is not permissible to use deception to take what one does not deserve, and the state's conditions for eligibility for housing or money must be adhered to. If the allowance is a grant from the state, then it is not permissible to use deception to obtain it. If it is compensation, then it is a right for the heirs, and they may use legitimate means to claim it.