Search the threads using +purchase +money +HELOCs as the search term and you will find tons of previous discussions on this topic.
To support what Kathleen stated you will need to look to the Commentary for 226.15(f). The initial advance that qualifies as a residential mortgage transaction, see 226.2(a)(24) for its definition, is exempt from the ROR but all subsequent advances would not be.
_________________________
The opinions expressed are mine and they are not to be taken as legal advice.