Old x86 Macs with non-intel GPUs tend to be a dice roll. I only pick up old models with intel integrated, as none of them are built to be serviced, and you need specific replacements for the ones that are.
They're neat machines, but even old ones hold a premium over contemporaries.
I'd also avoid any older laptop with a dedicated GPU. Particularly Apple, but I'd say it applies to every other manufacturer too considering how little thought they generally put into sufficient cooling. I've seen way too many laptops with defective dGPUs.
They're neat machines, but even old ones hold a premium over contemporaries.