Two friends and I lived at Karl's place for a summer - and our experience there was great! Karl was super quick to respond to any of our inquiries, and our neighbors upstairs were always helpful. The place was a nice 10-15 minute walk from the nearest metro station, and 5-10 minutes from several bus stations. We all commuted to work each day with ease.
The neighborhood was really nice, full of friendly people and nearby several park areas/coffee shops. The basement was truly a comfy oasis! All around, we had a wonderful stay - and I would definitely recommend this place to anyone interested in spending time in DC, whether for a couple days or a whole summer :)
Karl is genuinely a great host, and his responsiveness, communication, and helpfulness really made our stay.