numberOfAccommodationUnits

This term is proposed for full integration into Schema.org, pending implementation feedback and adoption from applications and websites.

Thing > Property > numberOfAccommodationUnits

Indicates the total (available plus unavailable) number of accommodation units in an ApartmentComplex, or the number of accommodation units for a specific FloorPlan (within its specific ApartmentComplex). See also numberOfAvailableAccommodationUnits.
Values expected to be one of these types
QuantitativeValue
Used on these types
ApartmentComplex
FloorPlan

Source

https://github.com/schemaorg/schemaorg/issues/2373