-(으)니까 gives a reason and 나가다 is going out or leaving: 한국은 너무 습하니까 나가면 바로 땀을 흘리고, 감기 걸리면 안 되니까 나가. Said to someone directly it can be blunt to the point of dismissal — 가족들끼리 모임이니까 나가세요! is "this is family only, so please leave." Note that -니까 also attaches to 보다 to mean "having looked at it," which is a different thing sitting in the same shape: 노동 시장을 보니까 나가면 안 될 것 같죠?.