I have only seen a/c units mounted like yours while visiting in upstate
NY. I assume it is for snow, which is not too much of a problem here in
south Texas. However, if you are paying for a new house, you are
entitled to have it fixed right. Putting the unit on patio blocks,
crushed stone or whatever, is not right. Vibration noises inside are not
right either. Insist that the builder get the A/C contractor make it to
your satisfaction, period.