I have a room in Botafogo, I usually rent for international students from FGV (Fundacao Getulio Vargas) business school. Usually master and doctoral students.
It is a small room, but with private bathroom, Internet Wifi and air conditioner.
I live there with my girlfriend, my brother and his girlfriend. Although it seems to be quite a lot of people, the appartment is big, has 3 floors, and we have separate rooms. It is quiet, clean and near Botafogo Metro station and Botafogo Shopping Mall.
If you are interested, I can give you more details.