The requirements of this section apply to open-end credit plans secured by the consumer's dwelling.
Also note the above cite states
secured by the consumer's dwelling. You will notice the word
primary is not included in that statement.
If the consumer uses a 1-4 rental to secure a consumer purpose open-end credit then 226.5b applies. So don't let the LO try to skirt the issue by claiming the dwelling is non-owner occupied.