I think this builder bought out a QLD builder, but the QLD branch doesn't get such good reviews as the original SA one. They are Rivergum Homes. They aren't the cheapest *or* the most expensive we looked at.
Not sure where 5 days comes from. We were told 9-10 months and we are at month 4 now. It is an inordinately slow process. We haven't even chosen our colours/taps/carpet yet, nor has it gone to council, where it will sit for more months waiting approval. Our subdivision to get the land to build this place took us near on 18 months but we weren't exactly rushing things ...
I'd imagine it is only a few days to put the house on site though, depending on how fast you can rouse Telstra, a plumber and your water corp. You need to prep the site first, with dolomite over compacted soil. And how your soil test comes back, they do different stumps on some soil types.