Wheatworks SoftwareТ‘s Rent vs. Buy Calculator 32 looks at this common decision from an investment value perspective. By calculating the gain or loss achieved by purchasing a property instead of renting it, the Rent vs. Buy Calculator 32 helps determine the net investment value of the purchase. Net investment value is given as the sum of the rental value of a property plus its appreciation minus the cost of purchasing the property plus the annualized cost of selling it. This is simply a "quick and dirty" way of looking at the rent vs. buy decision.