1. (a) Mortgage means and includes an instrument in writing which imposes a lien on or affects the title to real property or both real and personal property with such property being used as a security for the payment of money or the performance of an obligation, and includes an executory contract for the sale of real property or both real and personal property under which the purchaser has, or is entitled to, possession of the real property prior to the delivery of a deed. The term mortgage shall also include a contract or agreement by which the indebtedness secured by any mortgage is increased or added to, and a contract or agreement pursuant to which “new funds,” as defined at section 641.9 of this Part, are advanced or re-advanced under a prior recorded mortgage of real property. The term mortgage also includes an assignment of rents to accrue from tenancies, subtenancies, leases or subleases, but only with respect to real property located within any city in New York State having a population of one million or more.

2. (b) The following are examples of instruments which are mortgages when given as security for a debt or the performance of an obligation:

   1. (1) an instrument in the form of an absolute deed, which in fact is merely security;
   2. (2) an instrument which shows, by its own terms or by reference to other instruments, that the purchase price for the real property has not been fully paid, unless the vendor's lien has been waived by taking back a purchase money mortgage, by having the vendee assume a preexisting mortgage, or otherwise. The unpaid purchase price may be in the form of money, debts of the grantor assumed by the grantee (other than mortgages and taxes on the property conveyed), an annuity to be paid, or support or maintenance to be provided for the grantor or otherwise;
   3. (3) an instrument pledging the lessee's interest in a lease;
   4. (4) an instrument pledging the vendee's interest in an executory contract for the sale of real property;
   5. (5) an instrument pledging an interest in a decedent's estate, consisting partly or wholly of real property;
   6. (6) an instrument in which the provisions for lease and for an executory contract of sale are so blended as to be inseparable;
   7. (7) an agreement to make a mortgage on real property (but this does not include a provision for giving a purchase money mortgage, included in an executory contract for the sale of real property);
   8. (8) an agreement not to record a mortgage; and
   9. (9) an agreement not to transfer, sell, convey or otherwise encumber real property, otherwise known as a negative pledge agreement, but only if the agreement is actually recorded.

3. (c) The following are examples of instruments or agreements which are not mortgages:

   1. (1) an instrument pledging the vendor's interest in an executory contract for the sale of real property;
   2. (2) an instrument wherein a life estate is reserved to the grantor or other person and there is no obligation to support or maintain; and
   3. (3) an instrument creating lien by a judgment, mechanic's lien, or the filing of a surety bond and undertaking under section 2503 of the Civil Practice Law and Rules.

Tax Law, § 250