I hope you won't need all of it, a 20% down payment of $155k makes it a $775k house! Put the amount that is 20% of the house you might buy - ie, if a $400k house, then put $80k of it - into a high yield savings account and put the rest into your investments according to your target allocation. At current and immediately foreseeable mortgage rates that makes more sense than minimizing your mortgage, in my opinion.