

I don’t know the exact agreement with your friends, but to avoid security issues I personally would use following way:
- deny usage of all ports by firewall
- allow only necessary ports by firewall
- enable privileged ports by sysctl
So it reduces additional layers and complexity.
If one of your friends would provide a service on a specific port it has to be discussed with you.
And if this is a privileged port, it is also possible.
Or you can handle e.g. a web request with a rule in caddy.

@bordam Personally I would suggest, take so much Ram as you have money available.
If you have services relying on databases like Nextcloud (Valkey / Redis, MariaDB / PostgreSQL) more RAM could be helpful.
My current not finished setup with podman containers already takes 2 GB Ram.
Also prices for Ram and SSDs are predicted to rise or are already rising, so if you buy now, I would suggest to buy maximal large hardware parts.