Goodness I hope to never buy house someone used to hack into a smart home. I don't want to inherit anyones bugs or try to understand their mental framework for setting things up.
At least you have the capability of getting things into a working state without the original owner, which may be impossible otherwise.
Now of course the best case scenario is when the "smartness" is only additive to the home, and not required for it.
In my case, if Home Assistant isn't working, the house just works like a normal house with all the wall switches functining as you would expect.
If I ever sold the house, I would give the new owner the Home Assistant instance, disable all my automations, but also tell them that I'm not going to help them at all with supporting it. The most likely scenario is that they wouldn't want to use it or care about it, but at least the house works just fine without it.
Someday in the far future when someone buys my house, the small but noticeable differences in light switch behavior is going to drive them crazy. I did keep all the original switches for the next owner, if they are motivated to swap them back in.
Unlike some others in this thread, the 350 devices I have don’t require too much maintenance (have to replace the odd light bulb, and I do some upgrades once a week), and work flawlessly most of the time. I also designed it so that it works without home assistant or any controller.
But what I am going to do - some of the zigbee lights are permanently fixed, but are on manual switches so I guess thats ok. But the irrigation system, some of the lighting systems which are switched automatically, the built in speakers and even the networking might be beneficial to stay.
Would probably have to do an audit and take a couple of days.
I’d never buy a “smart house” though. I have to set up everything myself, that’s part of the fun.