[morid1n]

Not really. The biggest point of failure will be the drives and they’re universal. The only truly Mac-specific part is the motherboard and there’s plenty to choose from.

There is no Mac that supports my needs, used or new.

[wayoutthere]

Video cards as well; anything newer than High Sierra only supports AMD cards.

I'm genuinely curious -- what needs do you have that a used Mac would not support?