If you just want an app server pick up an hp elitedesk off ebay and a ups and run it on your home inet connection.
At least where I live there’s a stupid amount of red tape for these things.
And your home insurance will not know/care if you're operating a desktop-sized computer or even a single server (it is perfectly fine and expected a developer might bring an actual server home for troubleshooting). Home insurance only cares if you're running dozens of them.
You should be able to do this hassle free, and you probably can get away with it, but you may find yourself in a grey area later.
It's just one of many types of red tape that stiffles innovation.
It actually is in some jurisdictions, even if of course no one cares (except of course insurances looking for reasons to refuse a claim).
My ISP has a static IP option for £5/month, but I reckon I can save £30/month+ on server costs even before any rises.
Ofc it does mean I have to do my own sysadmining, but a combination of my general knowledge + an LLM should make that relatively easy.
If you just want to pilot a 747, drive your car really fast at a skate ramp.
A 747 is overkill for a fetching some groceries..