Yifan's place was simply wonderful! 10/10 on all accounts. His mother is one of the sweetest people you'll meet - very warm, welcoming and kind. She did a mini tour of their home and explained where to find what. Yifan himself was very prompt in replying to my messages, and very kindly offered to store my luggage as well, post the check-out time.
The room and amenities were perfect and exactly as described. The location itself is very convenient - walking distance to Union Station, restaurants and the National Mall area.
I cannot ask for anything better. Will 100% recommend to everyone and will again stay there next time I'm in DC. They've definitely raised the bar for all other AirBnBs. :)