To attempt answering it, assume that your local community went anarchic and all common services, local council, municipal, borough, departement, amt, district, oblast, region etc ceased functioning effectively immediately and would dissolve.
Discussion
Yeah. I get that. But still too many unknowns.
Firstly I expect in that situation that public goods solutions will exists on commercial basis (roads etc).
Then you're left with charity basically.
And In that case we are back to what I mentioned before, who, how, why.
But if I would have to answer the question regardless all the uncertainty and so on?
I would aim around 10%.