We are both in our early 80's. Believe me you will be happier if you don't have to do a lot of stairs as you get older. We sold or big house and bought a smaller one, all on one level and if we hadn't done that I would be in a rest home because I can't do stairs very well, or stand for a long time, or walk a long distance. As it is everything is close and I can work a bit and rest and work again and keep things decent. Several of our close friends and relatives are going through the same thing right now. Plan your first floor as your main dwelling area and the upstairs area can be for guests and occasional use.