What if they discover knob and tube wiring and you have to replace.

How much knob and tube wiring?

I'm not sure how it is in TX but in RVA if you touch/try to tie in new wiring to any of the existing knob and tube wiring, that has been grandfathered in, you have to rewire the whole thing.

That doesn’t even take into account that the boiler may be 100 years old, knob and tube could be present, etc. 

Not to mention, if you don't use it for a while, you get mildew in the tubes which gets shot all over the place when you DO use it. 

Also in this case it is to prevent a lender from denying the loan on a property with knob and tube.

You can just get a tube of sealant and do it yourself. 

I learned on You Tube and every where else I could. 

Royce, this is a 100 year old house and the house had knob and tube wiring on the second and third floor.

I have no idea and I suspect California mostly and or LA will be a part test tube proving ground and answer some of those cities or states banking concerns.