There seems to be a lot going on in this situation. You need to determine if this is truly a business purpose transaction (https://www.bankersonline.com/regs/12-1026/12-1026-003.html). If it is exempt from Reg Z as a business purpose loan, the collateral will not cause it to become applicable to Reg Z. See the commentary below:
Official Interpretation
Section 1026.23—Right of Rescission
1. Transactions not covered. Credit extensions that are not subject to the regulation are not covered by §1026.23 even if a customer’s principal dwelling is the collateral securing the credit. For example, the right of rescission does not apply to a business purpose loan, even though the loan is secured by the customer’s principal dwelling.
If you have additional information or if you determine this is not a business purpose transaction please let me know.