The wiring inside that BX shielding may have deteriorating cloth insulation and the size of the electrical service might be 60 or 100 amps and insufficient for a modern house. 

If you want to address this issue for the future, insulate those pipes in the attic and add some heat tape.

Cold air coming in around heaters, counters, or mechanical areas can indicate gaps in insulation or sealing that affect comfort and energy efficiency, so it’s worth inspecting.

If have access to the water shut off, make sure they know where it is incase they notice a burst.It's too late now, but going forward if you have any areas where pipes are exposed,  I would recommend heat tape combined with pipe insulation.

I’m not suggesting this would insulate you from future experiences like the one you had with Garnaco, but hiring a legit general contractor on the front end to put some eyes on the project/budget seems wise.

I’ve seen it come from everything from old duct insulation and past pest issues to moisture in the system or a disconnected return pulling from an attic or crawlspace.

We also put in a lot of insulation this fall that did keep pipes from freezing while some in the area did have issues. 

The floors and footings have to be specifically insulated, certain thickness, etc. 

I spent about 15k to repair pipes, remediation of mold, fix drywall, new insulation.  

Older homes from the early 1900s can be great investments but only if you know what you’re buying and price the risk correctly, because the big-ticket items you mentioned like knob-and-tube wiring, galvanized plumbing, stone foundations, and poor insulation are real and can get expensive fast if missed.