What does adding 'も=also' have to do when と alone seems to convey the complete meaning perfectly?


**Edit:**

> 新築の家を買った。今週を限りにこのマンション **とも** お別れだ。

According to a thankfully posted comment, I realized that
新築の家を買った。今週を限りにこのマンション **と ~~も~~** お別れだ。seems to be sufficient and も adds the
sense of 'also'.

How was that 'sense' expected to be added?....How was it figured out that it's
a suitable time to add the sense of も to the sentence?

