Sorry to continue our drift but, Jeri, in view of what you said, I will try to look for a reasonable on-line guide for you. IMO (and I admit to not being expert), if you really screw up at that level, to change you may be asked to move the foundations of the house but: if that level is reasonable, the worst you are likley to face is being asked to move a partition wall within the house. Hope that makes some sense.

Jon