If you can't afford to run a fedi instance then you can just stop. Users can migrate and the network will keep working just fine, that's sort of the point
Instead of exploiting users with "safe", "GDPR compliant" advertising, you could ask them to support you directly. If they aren't willing to then maybe it wasn't worthwhile to provide the service in the first place
It may be Joe's site, but everyone is welcome! A general instance with an emphasis on maintaining an open Fediverse and common sense community moderation. Rules are simple and aim not to be too restrictive.
If you can't afford to run a fedi instance then you can just stop. Users can migrate and the network will keep working just fine, that's sort of the point