1. The taxi fare from the Airport to the house
DCA: about $30-40, IAD: about $70-80 including 10% of tip
2. House/Room: High quality wi-fi, very clean, private and quiet room, spacious house with elaborate decorations, Perfect!!!!! nothing to say more
3. Location: It is a little bit far from the center of the cities, but there is a bus stop that connects to the attraction such as White house in a easy walking distance. I could feel the delightfully fresh air during the walk. :)
4. The Host: Very friendly and helpful. Actually, I've lost my way in the deep night on the way to return the home. I called the host, and she woke up because of me. However, they didn't blamed for me, rather they picked me up by car and tried to make me relaxed. Thank you so much :'(

I'd like to advice you not to get around in the late night, if you don't have a car.