There are a couple of factors that you must consider in order to get a good answer to this question. First what is your financial situation? If you are independently wealthy and can afford to pay for it in cash, in full, then that would be your best option. For an easy estimate, just figure for a 30 year loan, when its all paid off, it'll be double the cost of the house. So for your $500K, at the end of your 30 year loan, you'll have paid over $1,000,000. But you also have to consider the fact that the house will most likely be worth at least that too. Now if you're not independently wealthy, then you need to determine how much you can comfortably put down. So that down payment will fall in between a range of $100,000 (20%) and less than $500,000 (Paid-In-Full). So you 'll need to talk with your mortgage broker to determine what amounts will reduce interest rates. Do the math and determine what you're comfortable with. Another factor to consider is the length of the loan. The shorter the loan, the higher the monthly payments. But you will save a considerable amount in the long run. If it's an investment property, then you will need 25% down and be able to have enough in reserve to cover other assets for descent amount of time (3 months reserves for your primary residence. 6 months for each other investment property.) So in short speak with your lender about what's best for you financially.
I eat down payments for breakfast