Second Service Address on Same Account

I see that similar questions have been asked and answered but want to be sure...

I have a xfinity account for my primary residence in Auburn. Fine.

I'm also renting a space from a family in Hooksett. They are already xfinity customers. They have a drop and a modem in their cellar.

So as to have my own, separate modem and billing, I'm curious if I could add a second service to my account? The new modem would be co-located with the existing modem in their cellar.

How would my second service address be distinguished from their existing residential service that is already there? They both would have the same street address - from a billing point, how do you tell them apart?

If this is feasible, what's my next step to get this going? If it matters, just looking for internet (not tv or phone).

Thanks in advance!