Had the same question a year ago, researched quite a few options. Ended up buying used micro server (Fujitsu Primergy 120 S3) for around £30. Then upgraded it with low power 8 core Xeon and slowly maxed out it’s RAM. Currently it runs Proxmox with a dozen of LXC containers, Go/Node.js web apps and static websites using Caddy, mostly for home usage, only a few exposed to the internet using free Cloudflared tunnels. It also has a few VMs with k8s cluster just for the experiments. Overall I am very happy with this small setup, as a frontend developer transitioning into backend development it helped me significantly to improve my skills. I also sleep well as I don’t need to worry about spinning up quite expensive AWS services incorrectly and taking a mortgage after just to cover my learning mistakes. The only downside, though is that now you need to setup backup and pay for the electricity a little bit more than what Raspberry Pi will cost. But it’s still much much less than the price of around 20 VPSs you might buy at Vultr or Digital Ocean per month.