Just an outline of the foundation is needed. I build the whole foundation, then delete all but the outer row and add floor, but you need to delete only one or two rows at a time otherwise you can't replace the floor. By doing this (deleting foundation) you can save a little bit of money, not a lot, but still a saving is a saving. I don't think you loose money on building, I'm pretty sure that when you demolish, you get back the original price.
As for basements, you can build them later with a full foundation or just the outline. If you have a full foundation, you will have to demolish some of it to add the stairs though. Whichever you have though, the stairs will need to be done in two stages. The first one from the floor to the ground, then the second one from the ground to the basement floor. Actually, I like that, because you can have stairs that go down a little way, then make a right angled turn before continuing down.
Norma
