[pewu]

I wouldn't suggest hosting publicly open services from own local network. Without proper maintenance and experience, this is asking for trouble imo. VPSes are so cheap these days (far cheaper than 10$ if you don't need much performance), I'd recommend leaving local network out of the question.

When searching for cheap VPS, I usually peruse https://www.serverhunter.com/

[kimbernator]

I think it's a useful exercise in simple port forwarding, proxying (via nginx, for example), and certificate management. So long as you're not serving port 80 beyond redirecting to 443 and those are the only two ports being forwarded to the pi, it's really not that risky.