Final answer:
The lien a seller makes to assist with a buyer's down payment is considered a purchase money mortgage, in which the seller provides the loan and secures it with the property.
Step-by-step explanation:
When a seller makes a loan to the buyer to assist with the down payment and secures that loan with a lien on the property, such a lien is considered a purchase money mortgage. A purchase money mortgage occurs when the seller of the property provides financing to the purchaser, who then secures the loan with the property that is being purchased. In this arrangement, the seller essentially acts as the lender. This is contrasted with an installment note, which is a loan that requires regular payments over time; a special assessment, which is a charge for improvements levied by a government entity; and a blanket mortgage, which is a loan that covers more than one piece of property.