I would suggest you get reliable figures for Paoli rental properties and consider the following when 'crunching the numbers'.
The GRM formula uses the monthly potential rental income and doesn't account for a vacancy factor which could have an impact on the accuracy of the property value estimates. Many investors understand the above limitations and uses the gross rent multiplier to get a quick feel for the potential market value of an income property.
The GRM is sometimes calculated using the effective gross income rather then the potential rental income thus incorporating the vacancy factor in the GRM calculation. Effective Gross income equals potential rental income minus the vacancy amount. When vacancy rates are a factor, using the effective gross income will produce a more reliable estimate.
The capitalization rate is a more reliable tool for estimating the value of income producing properties since vacancy amount and operating expenses are included in the cap rate calculation. The GRM is useful in providing a rough estimate of value.