This has always been an awkward question. Section 1026.18(s) deals with closed-end credit. Your transaction is open-end credit. All the same, guidance from 1026.18(s) is used to determine the presence of a balloon payment.
Section 1026.18(s) defines a balloon payment as one that is more than two times the regular periodic payment. In the HELOC rules, Section 1026.40(d)(5)(ii) states, “A balloon payment results if paying the minimum periodic payments does not fully amortize the outstanding balance by a specified date or time, and the consumer must repay the entire outstanding balance at such time.” The problem is that a transaction may be a balloon under Section 1026.40(d)(5)(ii), but may not be a balloon under Section 1026.18(s). For open-end credit, that requires a minimum payment of 5% of the outstanding balance plus accrued interest or $50, whichever is less. If the full outstanding balance is due at maturity that amount may be a balloon under Section 1026.40(d)(5)(ii), but may not be a balloon under Section 1026.18(s), if the final payment is $100 or less.