A refinance is not subject to the right of rescission unless the transaction involves new money. New money includes paying an existing debt that is not secured by the principal dwelling, the single family in your case.
Regulation Z is not clear as to whether the party acquiring the property under the land contract has the right to rescind or not. Even though that party does not acquire full title until the land contract is satisfied, the safe course of action to provide them with the right to rescind since they have acquired some interest in the property as payments are made under the contract.