a separate living space in or close to a larger home where an elderly (= older) parent, or elderly parents, can live

In five years of renting out our furnished mother-in-law suite, we have only had one month with no renter. 我们把配了家具的老人套房租出去，五年里只有一个月没有租客。

A mother-in-law apartment can be in a separate structure on the same lot, such as above a garage, or a freestanding structure of its own. 老人套房既可以是同一块地基上的独立居室，比如建在车库顶上，又可以是自带地基的独立结构。