1.I'm calling to ask if you have a vacant apartment.
我打电话来是想问你们这里是否有空房出租。
2.We had a lot of bother finding a vacant apartment.
我们费了不少周折才找到一套空闲的公寓房间。汤姆使他老师大伤脑筋。
3.If you are looking for somewhere to rent. I think there's a vacant apartment in my buiding.
如果你找地方租房的话，我住的这栋楼里有空的房子出租。