Appraisers develop an estimate of market rent for residential properties by ______ and comparing rents across the subject and comparable properties.

The correct answer focuses on the process of converting monthly rental income to annual dollars per room as a methodology for estimating market rent. Appraisers need to analyze rental income effectively to estimate what similar properties in the same market are earning. By breaking down the rents into a standardized format—annual dollars per room—they can more accurately compare the subject property to comparable ones. This approach helps normalize the data, making it easier to assess how the subject property stacks up against others in terms of rental income potential.

Using this method allows appraisers to look at properties with varying rental structures and identify trends, establish benchmarks, and derive insights into the overall rental market conditions. This standardization is essential especially in areas with diverse types of residential rentals, as it provides a clearer framework for comparison.

The other options, while potentially relevant to the broader appraisal process, do not directly pertain to the specific task of estimating market rent through comparison of rents. Evaluating property taxes, depreciation, or historical rental rates may inform an appraiser's broader understanding of a property’s value, but they do not provide the same direct methodology for estimating current market rents.