Need affordable prime lens

Because your shooting will be inside a small apartment, you may want to use a wide manual lens and 28mm f2.8 is most common. Minolta, Vivitar Series 1, Canon FD, Konica, Yashica, come to mind. But you may wish to pick a more common line such as Minolta, so you won't need to get a different adapter in case you ever decide to buy another lens.