For the purposes of this part, a blanket encumbrance shall be considered to mean a trust deed or mortgage or any other lien or encumbrance, mechanics’ lien or otherwise, securing or evidencing the payment of money and affecting land to be subdivided or affecting more than one lot or parcel of subdivided land, or an agreement affecting more than one such lot or parcel by which the owner or subdivider holds said subdivision under an option, contract to sell, or trust agreement.