If you're looking for an affordable stay, a few metro stops away from the the city, I will recommend hotel Pivovar. If you're travelling with a group you can also ask for information. The owner has more (guest)houses in the neighbourhood.
I rented out an apartment for a month in Prague, the Czech Republic. The metro stop I got off at and then walked fifteen minutes to my place was Vysocanska. It cost me $300 for a month. These apartments were built in 2005 so they were quite new. I shared the apartment with another American. We both had our own rooms and shared a dining room, bathroom, and kitchen.
My apartment also had a balcony which had a great view of the city of Prague. Downstairs there was a washer where I washed my clothes. Custom has it that you dry your clothes in your room by hanging it out.
