My wife and I are preparing to sell our house within the next year. We have already purchased a lot that we intend to build on. However, our plan is to rent my newly retired parents’ house and live there while we list/sell our current home and use the savings to both build our down payment and pay off my student loans.The biggest variable in all of this is how much we might clear from the sale of our house. That will determine how long we rent from my parents before building. Here’s the question – do I need a minimum of 20% down (including cash and lot equity) to begin construction assuming we do a construction-to-permanent loan? Ignore PMI in the equation.