The first consideration is always your internet speed. If you’re building a pc then you’re self hosting from house. In many countries the internet is ADSL meaning the upload is very slow but the download is fast. However for hosting you need fast upload. You’ll need a fibre connection to stream video from home.

I rent a server in the cloud to do self-hosting due to the subtle difference in my definition of hosting, being that I control the services and data they hold, not that they are literal hosted at home.

Beyond that consideration I’d say everything else is trial and error and you should experiment.

I personally use Dell SFF 7040/7050’s. They can have up to 64 GB of ram, use NVME, and have PCIe slots for expansion while still being lower power and profile.

That said, for a lot of public stuff, like this very instance, I use Linode.

I don’t think you need to build a computer for this. Just run Docker on whatever computer you have. A laptop is fine.

Yes, it’s a great idea. And I also do it myself. In fact, I’m not only self host all my services. I also host them at my home.

https://server.melroy.org including all the sub domains are all hosted on the same server.

You can just use a good ryzen computer with enough ram (start with 32 gb or something). With enough storage. Redundancy via raid. I personally use Proxmox with an Ubuntu 22.04 VM. However bare metal may be also fine.

Have fun!

Use docker, I’m running 25 docker containers on my Nas, 6 of them which are internet accessible with 8gb RAM. You don’t need a massive server/machine that costs 300$ a year to run. Somw co tainera are Adguard, Emby, Guacamole, firefly, etc Learn docker and have fun!

One think you need to check before is your upload speed. Without a good one, it will essentially be useless outside of your home.
As for the computer, definitely buy something that can do virtualization, I’ve heard that some motherboard can’t (never seen one, maybe it’s an old thing).
And last, even an old computer can be good for self-hosting, except the plex / jellyfin video, almost everything is static webpages with databases. You can upgrade later just by changing the components, add more storage… You can even copy your entire system to a new computer if you change entirely.

Is it a good idea to host so many services, both publically-accessible websites as well as services only available on my home network, from the same machine?

You can use Caddy’s reverse proxy to have easy https + not opening ports from your router and have something like plex.mydomain.com / mastodon.mydomain.com. And you’ll have no trouble hosting differents services from the same machines. I believe it is not a problem to have multiples services on the same computer.

What are the security considerations when self-hosting?

I’m not an expert, but never use the default password when installing a service. And keep your stuffs up to date. https is important too, but is often automatic when using a reverse proxy.

If you have more question no problems :)