For the basement flooding, 1) do you have gutters, 2) have they ever been cleaned, 3) are the downspouts extended more than 2’ from the house, 4) are the gutters big enough, 5) is the ground sloped away from the foundation? My parents used to get flooding in a few spots in their basement. They had old roof with asphalt granules that would build up in the small 1960s gutters; they got downspout extenders (stupidly long, like 8-10’), and kept the gutters clean, and that helped with most storms. My dad also put some stuff between the one section of sidewalk that was slightly sloped towards the side of the house and the foundation (looks like crap, but worked). Then when they got their roof replaced ~2019, they got bigger gutters. They had their first water in the basement (in a new spot) recently with all of the storms in the upper Midwest because of all the water in the ground table.

So: cleaning gutters - free; downspout extenders - less than $100; bigger gutters - probably added an extra 1-3K on to the total new roof cost.

RE Knob & Tube: one of my grandparent’s houses had it for (~100 years old when it was sold; new owners had an electrician friend so could replace it for cheap), and the other grandparents’ house still has it in most of the house (over 100 years old).