Forecasting interest rates when evaluating a multifamily listing?

[Faisal Tahiri]

I've gone through many multifamily listings, and rarely find something that's cashflow positive. The heaviest parameters have been: price, rent/unit and interest rate. I've been playing price and rent/unit for potentially overvalued or below-market rents but I haven't touched the interest rate. 

Is it a bad idea to assume interest rates will fall say, 2-years down the road and baking that into some of my assumptions?

Note: Have been looking at fourplexes in St Louis area in class B or C+