ARM rate adjustments are limited by:

The Department of Housing and Urban Development (HUD) is a government agency focused on national housing needs and policies, but it does not impose specific limits on ARM rate adjustments. While HUD regulates aspects of housing and mortgage practices, it does not directly control the terms of individual mortgage contracts, including the interest rate adjustments of ARMs.

Margins refer to the fixed percentage added to an index rate to determine the interest rate of an ARM, but they do not limit the adjustments themselves. Instead, margins are a component of how the interest rate is calculated after each adjustment period. Therefore, they do not serve as a cap on the rate changes but rather establish the baseline for the ARM's interest rate.

Fixed-rate mortgages maintain a constant interest rate throughout the life of the loan and are not subject to adjustments like ARMs. While they provide stability in payments, they do not influence the rate adjustments of ARMs, making them an irrelevant factor in determining how ARM rate changes are managed.