Sanding a floor is just too big a job to do by hand (unless you have very big arms and lots of time). Hiring an industrial sander is both relatively cheap and will result in a much better finish. If you are sanding a large room (living room, etc) it is a good idea to hire both a drum sander for the main floor area, as well as a smaller rotary sander for the edges of the room.
Smaller rooms can be tackled with just a rotary sander. Both types are widely available from high-street tool hire shops and will usually come complete with the three grades of paper needed: coarse, medium and fine.