Thank you Peter, v helpful and exactly the sort of reply I'm looking for.
Yes, building resources is about getting/obtaining/creating the things needed to build with, which will then feed into the actual building.
Do you think that complete self-sufficiency is possible? As things like clothes, new steel/iron tools and even straw would be difficult/impossible to create on a smallholding. Certainly some form of trade would be needed, and whilst barter (and even 'scrounging') would be preferable that will be heavily dependant on the locale. Cash-based trade seems to be the only way to go, and I'm not over-keen on this.
Perhaps a collective of smallholdings (each focussed on meeting its own food needs and generating something else - milk, wool, straw, fodder etc - to be traded locally with other smallholders. But, hey, I'm drifting off topic there!