If you're brave enough to open the hatch door, then a set of steps leads down into the bunker itself. Sadly, we don't know how big the shelter is, but according to the listing there's 1,800 square feet of interior in total, which likely takes all three spaces into account.
In need of a major cash injection, the buyer will need to arrange for water, electrics and a backup generator to be installed, before the bunker will be usable.