Homelab

You can usually find good rack mount servers used on like eBay for cheap. I’ve gotten two over the years. Both were good and still running to this day.

Usually you can pick them up at almost any price range. But they tend to start around $500 or so. And they are normal x86 processors usually older xeons. And then with that you can run something like proxmox. And get a decent number of cores.

Or. Alternatively. You can also pick up a tiny mini pc with like a ryzen chip that might have like 8 cores and 16 threads for only like $300 or so. I use one of these as my daughters computer and I am endlessly impressed. Like no power draw. Basically silent. And overall very inexpensive.

Raspberry pie are great. But the arm architecture can present challenges sometimes.

Skip the pi's

Grab a refurb mini pc off of amazon and max out the ram, and install proxmox. Should have a nice little sandbox for under 150.

For networking a decent PC with proxmox can be the whole lab. If you can run a server and 2 client machines, that's enough for most network testing.

If you want to go full hardware a decent PC and two low end HP workstations running win 10 will do.

You can lab it all out in software or build various networks.

I'd look for used SFF dell, hp or Lenovo machines. Or just get a server that can run four VMs.

Get a used PC, haswell or newer. Those can be found for less than 50 €. Upgrade it to 16 gb ram, install proxmox.

If you have an old PC, that could very well be a start. Otherwise, Dell Optiplex or Intel NUCs will be more powerful than Pi at the same price. Throw Proxmox on it and you have yourself a homeserver.