Clean your gutters and get the mesh tops installed so they don’t clog again

If you have a demand water heater you should flush it annually. Learn to do it yourself. It’s not difficult and the one time equipment cost is less than you’d pay a plumber to do it for you.

Check and replace the anode rod in your water heater. It’ll vastly extend the life of the unit, and will improve the quality of your water. If you have tankless, then be sure to descale it.

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.

If you’ve got a sump pump, check that it’s in good condition. It’s not a bad idea to have a backup pump and back up power.

It is worth putting ~1 cup of mild cleaning agent like distilled vinegar down your AC drain line every time you change the filter if you live in a humid area! All kinds of stuff can build up or live in that line leading to a clog, leading to a float switch cutoff or even a bit of mild flooding of your Aircon closet.