I've always had good luck with used PC's for LinuxCNC, mainly because i always use the "Enterprise" versions from Dell, HP, Lenovo, and Fujitsu.
Same with Mesa, i am sure i have Intel and RealTek network cards in use, none had any issues, ever.
Then again, i have several USB to LAN adapters that work fine with Mesa, Laptops and tablets that work fine with Mesa, etc, etc.
I would roughly say i had about 0.5% rate of not working/not usable PC's, and 30% rate of not usable laptops.
