$700 Budget, thinking of using a G5 as a base and working from there

Yo, decided I need a new computer and I’m hoping on building one for editing and homework 3D design, all of which Macs are great for. Someone is selling a G5 for $40, still runs so I can sell the parts for quite a little cash as well. Is $700 a good budget and is the G5 a good case? Also if anyone could build a part list that would be great, although I can do that myself as well