Cool.

I've known of people who live together in multi-family groups, usually along the lines of a hippie commune or a Christian lay community. They've not been poly as far as I know, but maybe they just kept it quiet. I still don't (knowingly) know any poly groups who live together and have kids.

I do like the idea of a multi-family group of some kind: multiple adult influences on the kids, babysitters available on tap, ease of babysitting in return without leaving your house, friends and game/activity partners readily available for both adults and kids, and the opportunity to apply division of labour and economy of scale to the childcare, cooking, and housework.

I think what I'd most like is not a large multi-family house, but something like the semi you describe, or a street where the group occupy multiple houses in the street, so you have your own space but can walk outside and find instant social life, like in college. I believe the Westboro Baptist Church own a street like that; it ought to be possible to imitate that aspect without imitating anything else they do.