All the big hotel chains are present in Brazil and you can spend as high as you like when it comes to room rates. A Google search for hotels is probably the quickest way of finding what you need.
When gathering prices make sure you are aware of any deposits or extra taxes you have to pay. These can add to the price of your hotel room significantly. Taxes of 10-15% on top of room rates are common so assume that this is being added to your bill.
In Rio many hotels do not allow you to take ‘visitors’ into your hotel room. Especially visitors you met at a bar called Help. Much of the tourism crime is reported by men who let visitors into their rooms and wake up the next morning with a very bad headache, vague recollections of paying for sex and a missing passport.
Hotels like all accommodation providers typically enforce minimum stay periods during the Carnival and New Year holidays. There is almost zero chance of avoiding this. As with all real estate it is location, location, location. The closer you are to the beach and the better the view the fatter your wallet will have to be. A view of Copacabana or Ipanema during Carnival is going to blow most of the travel budget. Actually if you can afford this view I doubt the word budget comes up in your conversations very often.