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It's so hard to find as to be unenforceable, but have you checked the "fair use policy" ?
There are a number of far-reaching get out clauses in there, but as I read it, you can (and there are plenty on here that do) run a personal web server for your own use. The key clause is probably;
2.2 You have an obligation to use our services for private, personal, and legitimate consumer purpos...
Failure to adhere to the policy may mean a loss of, or restriction to your Service
My own little server is set up such that it is not accessible via the web unless I unlock it remotely before even entering username and password, and it then auto-locks itself after a period of inactivity. So under normal conditions, you can't even tell it's there let alone get to the log-in screen! Generally, there's a bit too much paranoia regards people being able to access systems armed with just an IP address, but as soon as you start running a server, if it's visible you will eventually have someone attempt to hack it! *I've had more than one third-party hosted web-servers hacked over the years - they are definitely targets!
Easy as (Raspberry) Pi. My own little RPi compatible server runs a web server, streams media, and works as an always-on back-up server - almost maintenance free! Odd as it may seem, but if you are running an old Win PC as a web server then you would probably have to pay more attention to maintenance than with an SBC such as the Pi!
*Be a little careful what you do as some uses could bring you into the scope of GDPR
I currently run a forum on a host but the renewal is £80 so was wondering if I could run it from home. Not technically cause I know how to do it, but I dont want to end up getting shut down for breaking Vodafone t&c