I didn't know that you could do ray tracing on a C64/C128/. I bet that was a lot of work setting all of that up. how did you "networked" them together?
You can do anything - albeit at a certain scale and speed - with even a lowly 8-bit computer. Start with the basic building blocks. Write a simple arithmetic library. Use that to write more complicated operations - square root, trigonometric functions, exponents etc Use that to write a linear algebra library - matrix multiplication, inversion etc Use that to write fundamental operations of ray-tracing - sphere/plane intersection etc. By the time you write all these little layers the actual task of writing a ray tracer is pretty simple and you're only dealing with the abstractions of how to manage your geometry scene model, eye position, animations etc. But, obviously, you learn a whole lot more than just writing a script for Lightwave for example.
There were some surprisingly (to people who didn't live through that era) complex things done back in the 8-bit days. Full Pascal, C, Fortran, and COBOL compilers were available, for example. MP/M was a multi-tasking, multi-user version of CP/M. My summer job for two years of college was working on a clone of the UNIX typesetting tools troff and tbl for CP/M.
But, you gotta start somewhere and be brave enough to imagine that you CAN end up somewhere altogether more complex. Focus on the coding. Why do you think you need a new monitor when I can do so much with a 40x25 text screen displayed on a fuzzy little colour tv?
This is why I keep saying "stay focused". @whm, you just spent a bunch of time researching which 4K monitor/TV to get, when you can't even afford one now anyway. You'll need to do at least some of that research again when it comes time to buy since the market will have shifted, so the effort was partly wasted.
You could've been making progress on your stated goal -- learning how to program -- instead.
If you really feel you need more screen space, use your laptop to pull up documentation, and code on your desktop; or set up dual-head with a second-hand monitor like I suggested before. Free (or nearly free), and no research required. As I've already noted, I only use a 4K at work because I didn't have to pay for it; at home I have a cheap 21" 1080p and a couple of ancient 17" SXGA (1280x1024) LCDs in triple head... and I have a decently paying full-time job, so I am not as budget constrained as you are.