Our rough threshold: a very short ARM, something like a 6-month ARM, would need to price around two full points below a 7-year ARM before it is worth considering, and even then only for the right borrower. A 6-month ARM starts adjusting almost immediately, so you carry rate risk from day one. These short ARMs got marketed hard by some call centers on the pitch that borrowers would refinance into a fixed rate within a few months once rates fell. When rates kept climbing instead, some of those loans ratcheted up several points within a handful of adjustments, turning a low teaser start rate into a much higher one. In a rising-rate environment the product is genuinely risky. Who it can fit: a buyer with a large down payment, strong credit, a considered view that rates are heading lower, and the finances to absorb being wrong. A modest monthly saving, say a few hundred dollars, does not cover the downside if you cannot refinance out in time. One mechanical note: these ARMs typically index to SOFR, the benchmark that replaced LIBOR, and SOFR tracks the Fed funds rate closely. The product's fate is tied to short-term Fed policy, which is exactly the thing nobody can promise. For most first-time buyers, this is the wrong tool.