Cathy, do you mean "build their own house" as in "with their own hands"? Aaargh! If you did that, the more power to you. We stood idly by 6 years ago and watched our beautiful home rising from the slab. That's as close as we got to "building" it. But it all works out the same, I guess.
Best of luck to you both in your soon-to-be new home!