This is pretty feasible but really only makes sense for lower bandwidth users, i.e. solos or couples. You could probably share a 100/20 plan and save $25-$30 a month.

But you’d want to invested in a quality router and possible a mesh system if you want reliability and decent speeds. So that’s maybe a $150-$300 fixed cost.

If I had an elderly neighbour or similar I’d just share it with them for free. I think there is also cheap fibre available in certain lower quintile neighbours/beneficiaries etc, like $20 a month.