Is it permissible, Islamically, for a sister to pay her brother's share of the inheritance in monthly installments, given her fear of her income stopping and her inability to pay in the future?

It is permissible for a sister to buy her brother's share in an inherited house and pay him the price in known installments. Her fear of her income stopping and her inability to pay does not prevent her from buying, as long as her brother is aware of her situation and has agreed to that.