or they can't afford more than an existing hand-me-down PC.
Or better yet you do as I have done. Buy an off-lease Lenovo Thinkpad for $150.00 or so [...] and if you really need Wi-Fi a $10 Netgear WG111V3 will always work in Linux
That's good to know for people with $160 for a project. I too have had good luck with GNU/Linux on an off-lease ThinkPad, needing only to install the proprietary firmware for iwlwifi. But in this particular case, a hand-me-down PC with a hand-me-down Windows license is $0, which is $160 less and which is all my source was willing to spend on an experimental PC to run retro games.
I really don't like using Wi-Fi though, as all of the 11 channels are super congested already in most locations, and even if they are not, an Ethernet connection to the router is much faster!
A 400 foot (122 m) cable run to the basement where my source is staying (long story including disinheritance) is more than $0, as it needs a switch in the middle to repeat the signal. And my source found that one of his five WLAN could get a signal in the less congested 5 GHz band (as can the off-lease ThinkPad I tried).