Seller Financing - 2nd Mortgage on other property as collateral?

[John B.]

Hello, first post here.

Selling two parcels with seller financing.  Buyer proposes the following structure:

Parcel A: Buyer puts 50% down at close, seller finances the remainder.

Parcel B: Buyer puts 0 down and no interest due for 6mo, seller has 6mo to cancel if better offer comes along and no interest is due if cancelled by seller.  Buyer is locked in and does not have the option to cancel.  Buyers performance on parcel B is secured with a 2nd mortgage (note and deed of trust) against parcel A - with an cancellation clause for seller without penalty or payment within 6mo.

Own both parcels outright, no houses on parcel A, renter owns a mobile home on parcel B and the contract stipulates they can finish their lease on parcel B.

Does this appear to be a secure approach with parcel B? What to watch out for here?  Are there pitfalls that arent apparent?  Not using a lease option on parcel B in order to ensure that buyer doesnt just tie up the property for 6mo and then back out.  Buyer is proposing this in order to try to stretch into both pieces of property with anticipated income from another property sale, while keeping seller happy.  Buyer says they are not able to get bank financing on raw land.

Any input or insights greatly appreciated.