[ConservativeMind]

Yes. In our area, our phone lines had a bunch of extra wires and another DSL line could be created out of those. So you pay for another DSL line with Internet, but now you use half as much over the month from each, so if you had 1 TB without surcharge, you have 2 TB.

There are modems and routers that can negotiate your communications in a transparent manner. Worst case is two separate computers having their own full speed DSL, but not having to do anything to achieve that, as it is automatic.

[Yosemitest]

The reason I decided to drop AT&T was a storm that blew down some trees that uprooted their phone lines a couple of miles up the road.
It took AT&T a little over two weeks to fix the line and return our phone service and internet service to operating condition.
My dad's in his mid 80s and that's too long to be without a phone, in case he needs medical attention.