Two pieces of advice:

• never buy hardware online, except from a vendor you know and trust (don’t browse amazon/ebay because it’s full of shit)
• never buy hardware less than 1-3 years old, because firmware/drivers are not mature yet, but hardware has great chances of having major issues soon (wild estimate: i’d say 75% of models are entire shit that will end up in the trash in the next 3 years, but the 25% who stood the test of time likely will survive another decade)

There’s a lot of good, reliable vendors for second-hand hardware. If your friend wants to make an “ethical” purchase, i’d recommend something like minifree.org. Those are solid second-hand hardware pre-loaded with libreboot, a cool project to replace proprietary UEFI/BIOS blobs. They are sold directly from people running the libreboot project as a means to support that effort. There’s a few other vendors providing equivalent services, i just cited this one because i saw it in the news yesterday.