I agree with your "minimum"
I have single storey 2 lounge, kitchen/dining, formal dining, DLUG + 2 undercover spots, 3 bed + study, ensuite, 3x4 b/s/t laundry + pool & big covered area at the back.and reckon it's small for 4 ppl.
Though according to some here it's a "monster" lol
20 squares is...