Well, it depends on the house. My foster parents built their own (passive solar) house (5 BR, 2 bath). But to do it, my foster father first spent a summer learning what he needed to know doing volunteer work for a construction company. My foster mother did the architectural design (not simple). Once they had the plans and the necessary expertise, they paid to have the foundation poured, then they got to work. There were three of them doing the work initially (foster father, foster mother, and their older son). Then they started taking in foster kids (like me!), for one more hand. With four people working part-time on the house (everyone had actual jobs too), it took two years until it was more or less complete. It was also about a half-million dollar home (in today's dollars), so it's roughly comparable to the home the Palins built in two months (while THEY were holding down jobs).
The materials for the house came from the same stores that the materials came from for that multi-million dollar complex, which was built after the Palin home was completed, and was only a mile or two away. So, from appearances, they dropped a bunch of stuff off at the Palin place, finished up that house, then got started on that multi-million dollar complex.
You can draw your own inferences. Maybe there's nothing to it. And maybe there is. I'm sure people are digging around trying to find out how much they paid for the house (if anything), and to whom (if they didn't get it for free, as an add-on to that big complex). If they got it free, well, it wasn't really free -- taxpayers paid for it.
