Which is not a typical unit of comparison for valuing an apartment building?

In the valuation of apartment buildings, the most common units of comparison include metrics like price per unit, price per square foot, and price per rentable square foot. These measures allow appraisers and investors to evaluate the value of properties based on their income-generating potential, size, and layout.

Price per unit is particularly relevant for multifamily dwellings, as it provides insight into per-apartment valuation, making comparisons across similar properties straightforward. Price per square foot and price per rentable square foot offer additional perspectives by taking the physical size of the building or the usable space into account, which is crucial in rental markets.

On the other hand, price per acre is generally more applicable in the context of land valuation rather than for specific improvements like apartment buildings. Most often, it is used in agricultural or development scenarios where the amount of land itself is the main concern, not the structures built upon it. As such, it is not considered a typical unit of comparison for valuing an apartment building, leading to its identification as the correct answer to the question.