I would not encourage someone who completely lacks experience in server/network management to do self-hosting, as it is easy to make mistakes.
Nevertheless, if someone is willing to dedicate some time for study and experimentation in the beginning, this is not an insurmountable problem.
I have been using self-hosting on "a literal PC in my basement" for about 20 years, without any problems whatsoever, and with negligible costs (the main cost being that I have a set of public IPv4 addresses and a fixed IPv4 address on my router connected to the ISP, which implied a more expensive monthly fee for the ISP).
After the first few months, during which I have made frequent changes in the configuration, while I understood better and better how it should work, the time wasted with server management during the next years has been negligible, i.e. just a few hours per year, used mainly for software or hardware upgrades.
Configuring and managing services just for personal needs or for the needs of a small number of users, e.g. a family, is much simpler than in an enterprise setting.
For reliability, it is good to have a second spare computer and a second image of the root SSD/HDD used on your server, to be able to replace the active server in case of failure. As others have already mentioned, periodic backups should be done and they should preferably be stored in a different location.
While I believe that self-hosting is not difficult, unless someone has already done such management work as a professional, it is necessary to learn many things.
For security, the first thing needed is to understand well what a firewall does, which are the firewall rules needed by whatever services you want to host and how to configure and monitor whatever firewall program you choose.
For this, some knowledge about how the main IP protocols for networking work is necessary.
The management of keys and certificates is also important, as you have mentioned, but what you need to learn for this is much less than what you need to learn about networking protocols, in order to both make a correct server configuration in the beginning and to diagnose any problems that might appear later (usually because someone at your ISP makes some changes in their configuration, which break yours, but nobody who answers the support call has any idea that they have changed anything, so you should better be able to identify yourself what they might have done, if you want a quick solution).