key money
noun
mass noun
1- informal money paid to a landlord as an inducement, by a person wishing to rent a property〈非正式〉（为取得租赁权而付给房东的）小费。
1.1
- Brit. a payment required from a new tenant of rented accommodation in exchange for the provision of a key to the premises〈英〉（新房客取钥匙时付的）保证金。