There is a guest house next to the training building of Beihang University. The conditions are good, but it's expensive. The standard room is about 200, depending on your ability.
Beike is one stop away from Beihang University, and Building 4 inside is also a guest house, which is open to the outside world. The conditions are similar to those of Beihang Guest House, and the hotel-style management is very comfortable. However, the room layout is that two rooms share a bathroom, so it is cheaper. Generally, he gives a 30% discount, which is about 70 for a small single room and 90 for a large double room, which is acceptable. However, it's a long way from there to Beihang University, so it's recommended to take a bus.