Trended rents are rental rates that are based on market growth projections for inflation and other factors. Usually, historical market data is used to predict future rental growth of annual rents. While using trended rents may present a slightly more accurate version of a property’s future financial position than using untrended rents, it’s usually not a good idea to rely on future rent increases in order to make a property profitable.
Untrended rents are projected rents that are not based on market-driven rent increases. In contrast to trended rents, untrended rents assume no growth in annual rents. While it's true that rents are growing in most areas in the United States, using untrended rents in projections is a safer and more conservative way to calculate the future financial position of a multifamily property investment.