Key money - A cash payment paid to a existing tenant who assign their lease to a third party where the rent is below market, possibly in an area with strict rent controls.

Kiting - An illegal practice of writing a check against insufficient funds that takes advantage of the float, the time between when a check is written and deposited in one back and when it is presented for colllection at another bank.

Knock-down - To assign a sale to a bidder at a property auction by a knock or blow of the auctioneer's hammer, or by any audible or visible announcement signifying to the bidder that he has the winning bid and is entitled to the property.