I spent two nights at Sa Rang Chae Guesthouse and seriously considered changing my itinerary to stay longer.
A traditional guest house, that requires you to sleep on a thin mattress on the floor, which proved comfortable enough. The walls are thin so be prepared for to overhear your neighbour. My room had it's own toilet and shower both of which worked well but some rooms share a toilet/shower block. I'm in my 50's but felt a definite student atmosphere to the place. Breakfast is provided in the form of bread, butter, jam and eggs which you cook yourself in a communal kitchen. This area also has a computer allowing internet access but free wi-fi was also provided. Meals can be eaten in the shared dining room or outside at tables where guests often congregated. There is a shared fridge, complete with sticky labels to mark your food. Departing guests often left stuff behind labelled 'free,' it was that sort of place. I think the house is well known for its dogs, one friendly, one less so, both clearly very used to having their photographs taken!
The owners were usually available, spoke reasonable English and proved happy to help with tourist advise, booking taxis or on one occasion give a lift (free.) They provide a washing service and laundered, but didn't iron, a basket of clothes for 5,000 won
The house practically borders a park holding a number of royal tombs, is about 10 minutes walk from the observatory. I'd estimate it at 15 minutes walk from the bus station, we arrived by train and the taxi fare to the house was 2,900 won (say £1.50) There are lots of shops and cheap restaurants within 5 minutes walk.
It was the cheapest place I stayed in Korea, my two nights and and one load of laundry costing 55,000 won (approx £27.50) we had booked two rooms so do not know if this led to a reduced rate. Most of my holiday was set in cities, all having a frantic pace of life, Sa Rang Chae was quiet, still and by far the most relaxing place I encountered in Korea. In the evening it was lovely to sit in the main courtyard with a couple of beers (purchased externally) and relax.