Down Payment Optimizer

Inspired by the raging bull that was driving the real estate prices in Rio de Janeiro to the sky between 2011-13, this Python script calculates the optimal down payment on a house.
The user inputs the value of the house; how much money is set aside; the expected interest on such money; monthly disposable income; the annual interest to be paid to the bank and the number of payments.
The script then gives the down payment value that optimizes either total amount of money after all is paid or the average monthly financial impact.