They aren't as expensive as you'd expect[1][2] ($70-$200). Hell, you could use a RPi for many use cases.
In my case, my homelab is my laptop (which I connect to from my desktop). I don't actually have a server blade lying around (although those can also be relatively cheap when big cloud upgrades their servers).
I pay 30$ a month for a server (yes, a virtual one, if you want docker, you have to pay a bit more) with org-domain and tls cert. I would recommend that to every developer. Yes, some administrative work is required but that is also a valuable learning experience. You would own all the tools that you need to develop efficiently.
Personally I use Gitea, which should be usable by someone used to Github. I don't switch workspaces too often, but I am sure some tools are available.
I have an HP 4u from 2010 with 80 threads and I think a quarter TB of memory, 6 SAS, and 2 1TB ssd, currently running Ubuntu 16 and Wok, for VMs. It took a lot of effort to get this working and it's still a huge pain - I have no UPS for it since it uses 220VAC, and UPS cost more than the server cost me, for example.
I can't use docker in general because my internet is too crappy. That was annoying in 2012 when I first used it, but it's even worse now. I've always worked with VMs, since 2001 or earlier - virtualbox, wok, AWS, wok, and now proxmox.
It helps to know what your use case is, I don't run a ton of VMs, just one or two at a time that can use almost all of the resources of the server, and I generally do infrastructure and computing work in general.
I presume none of this counts as a homelab, though, since I don't program in rust.
