If I’m not mistaken to make your instance available to other people you’d have to set up a reverse proxy. And a correctly set up reverse proxy shouldn’t reveal your IP, only the local IP (127.0.0.1).
I might be wrong, so ask on the !selfhosted@lemmy.world, since it’s more active than this community.
However renting a VPS and hosting your Lemmy instance there is probably a better idea if you plan on creating a community, since it will minimize risks (DMCA notices, bugs in the Lemmy source code that could expose your server, etc). And it would make scaling easier if your instance grows.
The thing is that right now it’s not worth it to buy a raspberry pi if you want to selfhost. It is 4 years old at this point but it cost 50% more than when it was released.