Of course you can always build a good PC or server.
I could have done that too, but I wanted my first real homelab-do-it-all-yourself setup to be a little more on the cautiously small side. I didn't want to have too much noise in my apartment and also didn't want to stress my electricity-bill and wallet too much, so I opted to build small and reuse what I had lying around.
I already had 2 Mini-PCs and a raspberry pi from earlier experiments with selfhosting. I just bought some disks and RAM. If you don't have any mini-PCs, they're relatively cheap in comparison with full PCs. Or you could use some older PC you still have but do not use.
My motto more or less was you can always spend more money and build bigger later
The final Hardware
- Mini-PC: Zotac ZBox CI665 nano
- RAM: 32 GB DDR4 RAM (according to specs, CI665 cannot go beyond 32GB sadly)
- SSD: 1x 2TB Samsung SATA SSD
- external USB HDD (6TB)
What I host on my Proxmox VE
- CheckMK Monitoring
- GitLab Runner
- pihole (network-wide, DNS-based adblocker)
- Nextcloud (production and staging instance for testing new updates before rolling out to production with my data)
- nginx proxy manager
- syncthing server
The 2nd Mini PC (some old intel NUC with 4 cores and 16 GB RAM) + a USB HDD is my Proxmox Backup Server for all this. And what's really important (my data from nextcloud + some configs) gets backed up to my Hetzner Storage Box with restic.
The raspberry pi is now my WiFi Access Point :)
Conclusion
Homelab doesn't need to be big or small, it can be whatever you want it to be or whatever you can afford or are willing to have and maintain. From my experience, if you're not hosting anything CPU-intensive, older or smaller machines will do just fine.
For example, my nextcloud could easily use more resources than the whole Zotac ZBox could house, if there were more users. But as my services are only used by me, most of them are idle most of the time.
Tip at the end about your opsense-VM on Proxmox
I tried letting Proxmox host my pfSense too, but that got old pretty fast. Whenever Proxmox needed a Reboot, my internet was gone too for that time, as the pfSense VM on Proxmox was the gateway to my ISP-modem. In the end, I just bought a real Netgate pfSense appliance.