Travelling around Brazil most of the time you'll find your accommodation in the form of pousadas, cheap guesthouses that will give you a room and breakfast for around $10.
In the big cities like Rio or Sao Paolo, though, it will only be in the rough areas of town that you'll find prices that low. Figure more on $15-25 for a budget hotel room, or $50-100 for a comfortable hotel.
If you're staying for a long time in any one spot you'll be recommended to get an apartment. Houses or apartments in Brazil will cost you are $130-200 in most parts of the country, climbing to $300-500 in the nicer areas in the cities.
Most apartments will have a porter on duty who doubles as security, receptionist and trouble shooter. Be nice to these guys, it's a shtty job and they could do with a tip once in a while. Then they might remember you when your upstairs neighbour starts practicing samba at 4 in the morning.