Make sure the responsible people in your household know where the main water, gas, electric shutoffs are and how to use them properly. For water and gas, make sure they still are accessible and work by actually turning them off then on.
Almost everything in a house has a lifespan. Know what it is and where yours is at in terms of life left. Different roofs, siding, HVAC systems etc all have different lifespans and odds are you're gonna have to replace most of them at some point in ownership.
Spend some hours on YouTube watching this old house or something similar. You'll learn a lot of random things that mashes people handy, even if it isn't directly applicable to your situation. How to replace a doorknob, how to change an outlet, unclog a drain, etc.