This is the 2129th most frequent Korean word.
월세
Monthly rent.
Here, 월세 is used to denote the monthly rent payment one is responsible for.
나는 이번 달 월세를 이미 냈습니다.
I already paid this month's rent.
In this sentence, 월세 refers to the amount charged for monthly rent of a specific place (the apartment).
그 아파트의 월세가 얼마나 되나요?
How much is the monthly rent for that apartment?
Here, 월세 signifies finding a rental option that has a lower monthly cost.