“首付”的英文表达是：Down payment （分期付款中的）头期款。
We are saving for a down payment on a house.
Now you've finally got enough money together to put a down payment on your dream home.
They have burdened themselves with a high mortgage.
We're having difficulty keeping up our mortgage payments.
We had to offer our house as a guarantee when getting the loan.
The bank is pressing us for repayment of the loan.