地下室
depends on what the 地下室 is, basement or cellar. if it is basement, it is legal, even for rental. it is illegal to live in the cellar.
将一楼大厅分为隔两间 - most likely, this is illegal conversion. dept of building will not approve this conversion if there is not sufficient natural light or ventilation in those two rooms.
将一楼大厅分为隔两间 - most likely, this is illegal conversion. dept of building will not approve this conversion if there is not sufficient natural light or ventilation in those two rooms.