Our current house has four to five feet. It isn't nearly enough. I would try and avoid having the stairs directly in front of the door at all. If there is a staircase off of the foyer, it would be best if it were to the side, so a visitor sees a welcoming path leading toward the main living area, instead of a climb to areas that are usually thought of as private.

I would say 6 feet minimum. I like to have the stairs going upstairs a fair distance from the front door -- just leaves more landing space there and gives a nicer "foyer" feeling.

Ours is 4'5", it's plenty of room. However, the staircase is not directly in front of the door, it is to the side. So, if someone where opening the door they wouldn't be standing in front of the stairs, they would be next to and slightly in front of them. The way the door swings makes a difference as well. When someone enters through the front door there is the foyer and hallway in front of them, not the stairs.