Depending on your age/how long you plan on living in the house, not a terrible idea to make the doorways wheelchair width.
That is what I was thinking too. Also, make sure you can get around in the kitchen with one. A lot of people are putting islands in their kitchen, make sure you can get around it. Also, don't forget about aging parents. One may need a bedroom on the bottom floor that is ready for them with a bathroom and shower that is wheelchair accessible.
Put enough faucets on the outside to be able to use a garden hose/pressure washer to wash the house down periodically.
