Adjustable-rate mortgages are complicated instruments. No one characteristic fully describes one. This is why, when readers ask me for the pros and cons of COFI ARMs, or Libor ARMs, or flexible payment ARMs, I get heartburn. You can't assess an ARM based on only one of its features.
But some features are more important than others. If any one feature deserves to be considered the "real price" of an ARM, it is the fully indexed rate, or FIR. Yet ironically, I have never had a reader ask me a question about the FIR. more...