I agree with the other poster. Not only is Intel Mac on the way out, the the Apple silicon chips are SO much more efficient in Macs, leading to longer battery life and less ram usage while doing stuff.
Best Buy has the base M3 MacBook Air on sale for about $750 right now. If you’re dead set on used, they have a handful of refurbished M1 Air and Pro models starting around $500.
This is also a great suggestion. Last year I got the then-new iPad Air with the M1 chip in it (Gen 5 I believe), and after getting a Logitech keyboard case it has completely replaced my laptop for work. I’m in sales so I don’t need it to do anything intensive, all I ask of it is to simultaneously run QuickBooks and Slack and a couple other apps I use to do my job, as well as hotspot to my work phone, and it does all of that really well. Recent updates to the iPad OS have made that transition way easier, and I can even set it up a base station if I need to by connecting my Bluetooth mouse and keyboard and a second monitor and that also works pretty well in a pinch.
All this to say, if your relative doesn’t need the computing power of a full computer and they already have an iPad, that could be an ideal direction to go in.