<prompt> Human: On one hand I think that its better to invest as little as possible in the house and profit from mortgage interest rate deduction when I do my taxes. is there a rule if thumb to determine how much I can save from that by the way?. With the money I didnt use for the down payment of the house, I can now invest in an IRA or in my 401k. Option 2 is to put a huge down payment , reduce my monthly payment and interest spent over the 15 or 30 yr term. With a lower monthly payment I can now save more every month and re invest the money. The cons are that all my cash is now inaccessible since its invested in real estate and that my mortgage interest rate deduction from my taxes is now lower.  <response>: You should put at a minimum 20 to avoid PMI. Beyond that it depends on the interest you get. 