couple of things: foundation health is hard to define. foundation condition is quite important. Drainage is the most important factor for us in the Mid-west and northwest. Always important. Of course, if you live on a slab of concrete then drainage loses some of it's importance. And - there are many components to a house foundation and any one could have a problem. Sill, plate, vapor barrier, wall, knee wall, floor post, pillar post, tile, gravel fasteners, material, type of wood, etc. Often it is just easy to tell them "you have a foundation therefore you will have a problem". Eventually.