Masayako, although few have discussed it here, you are borrowing today’s money at tomorrow’s prices. With hyper inflation on the horizon you are certainly in a better position putting less money down especially with the current rate of return on your current investments. I have been telling my clients to put as little down as possible if they have the ability to park that money elsewhere with a better return. I have two clients in escrow doing just that. Rental properties in areas like Temecula/Murrieta are still very solid investments.
4.5% is free money in my opinion. I think I even saw rates touch 4 3/8% today. Follow your own instincts and good luck with your purchase.