It is 100% a great idea to see how you feel about the concept of self-hosting with an old machine. If it’s really old (and I’m talking like anything from before about 2008-2010), perhaps consider snagging an old “tiny”/1L-class box from eBay for cheap. Dell, HP, and Lenovo units can be found for WAY under $100 all the time, and slightly more modern units can still be had at a reasonable price, depending on the model. They’re great platforms to play around with. Just shove a cheap SSD in there and play with it.
Source: an old m920q with an i5-8500T is running pfSense for my home network
I have a PII laptop from 1998 sitting around, still runs, don't have the heart to pitch it. But now you've got me thinking... That's a lot of juice.
Maybe it would be a neat experiment in using it via Wake-on-LAN from something else. But if it can wake from something else, that something else likely has more oomph anyway!