> Are these houses mostly built to be sold on completion, or occupied by their current owners?

In the US, only a minority of houses are build from the ground up by a specific person (custom houses).

Most houses are built like this: property developers buy a large plot of land, divide it into plots, and build a group of houses. From the moment they divide the land into plots, they pre-sell the houses. The earlier you buy in, the lower your price is.

Because of that, it's tricky to answer your question:

* Some of the houses may not be sold yet * Some of the houses may be under contract, but the buyer can back out by losing their down payment (especially in cases where they can't get financing - you can put a home under contract without the full financing secured) * Some of the houses may be fully sold, with the financing paperwork already secured