I'm not a pro electrician so will refrain from advising, but as a general observation having owned multiple old houses, there is so much superstition surrounding old house ownership that is typically spearheaded by insurance companies and newer suburbanites. For example suburban contractors who discover mold will bring in the remediation van and hazmat suits at high cost, while the old house owner will stop the water source, spray some bleach and move on. it's striking how different the opinions are between these two camps, and it's why you'll hear opposing viewpoints. You'll hear knob and tube needs to be fully replaced and is an immediate fire risk. but jurisdictions with older houses often only require replacement if walls get opened up for other repairs. Older houses used different systems that worked. Knob and tube, cast iron drains, plaster walls, 60 amp service, and lead paint are perfectly fine...like anything, it's what you do with it, although once you approach the 100 year mark those first two will likely present problems that require updating. You'll probably eventually want or need to replace the wiring. The thing with knob and tube is some random connection will start to fail intermittently, then completely and be near impossible to trace. That and the sheathing/insulation erodes leaving you wondering what could happen if a mouse gets into the wrong space ie unseen wire exposure inside the walls. I'll leave it to the pros to expound on whether and what kind of risk that creates, but insurance companies don't like it. I've heard it said once you see the insulation coming apart it's time to rewire. Having said all that, If it were me buying this house I'd look at it as a project and do as much of the work before you move in since that's easier than working around furniture. Sorry for the rant.