As anyone who follows mortgage rates day in and day out can tell you, rates can be very volatile at times. Who watches interest rates day in and day out? Bank loan officers and in particular the secondary department at the bank. The secondary rates for investment propertydepartment monitors rate movements all day long and if there are any sudden moves, the department quickly adjusts interest rates to reflect that movement.

But one interesting facet of mortgage rates and any fixed instrument for that matter—it takes a behemoth force to push rates lower and just a sneeze from a Fed official to have them shoot through the roof.

We’ve already been witness to the phenomenon this very year when it took nearly two years to get 30 year mortgage rates in the 3.50 percent range then last May, rates shot up by more than a full percentage point in less time than it takes to watch a season of Breaking Bad. If you’re in the middle of refinancing one of your rental properties or waiting to lock in a rate on a new acquisition, that sudden rate movement tells you something: if the rate is acceptable now, don’t wait to see if rates fall further. You could lose big.

For example, say you have a duplex with a 30 year mortgage of $250,000 and are sitting on a 5.00 percent rate. Today you might be able to get 4.50 percent, which would lower your monthly payment by about $75. Not bad, really. But you think you can get another ¼ percent if you just wait. The rate at 4.25 percent lowers the payment by another $37.

If you wait until next month, still clinging to the 5.00 rate, you already lost $75 by not taking the available 4.50 rate. Now turn the tables, what if rates rocket up by another full percentage point, what is the loss? At 6.00 percent, the payment increases by $156. You held out to gain another $37 yet rates left you and never looked back.

If rates are a good deal today, don’t wait for tomorrow.