Thanks for the answers Lena - further experimentation suggests that item transfer for sale is of fairly limited use, but it's good to know these things. Thanks also to Rainbow Dash for bringing my attention to the fact we don't have to stick exclusively to premade households! I'd assumed otherwise, even though as Lena says it's never specified in the rules. My game only ever seems to generate a handful of new families in Willow Creek and Oasis Springs, and though I'm not sure there'll be all too many that'll be more attractive propositions than some of the premades, it's worth a quick rejig of my strategy, I think...
Speaking of strategy, I've got two new questions! First: though my sim "cannot gain more than level 1" in a skill before designating it, presumably they can progress as far into level 1 as they like? As in, they can be 99% of the way to level 2 before designation? Second: can potions from the reward store be treated like fruit in previous examples, in that they can be purchased by one sim yet given to another to consume, even across households?