I've repaired all kinds of stuff in my house, including appliances. Calling someone to fix something could cost me more time than fixing it myself. Also, I can time-shift when I do it myself, for instance working during hours when I'm unlikely to get paid to do something.

An example is bike repair. If something breaks, getting it fixed would mean driving it to the shop and back again. Doing it on my own terms and schedule, I can fix it at night, often in a few minutes. If it needs a part, I ride a spare bike until the part arrives.

I decide on a case by case basis. I don't change the oil in my car because I can drop it off on my way to work, and in that case, I am getting paid while the car is being serviced. Also, some kinds of work involve more tools and space than I want to own. And mess.

The home furnace, in the middle of winter while my elderly parents are vising... yeah call the guy.