We wanted an apartment to accomdate 4 people (2 couples) during Carnaval in a great location and for a reasonable price and we got exactly that. We were one short block from the beach (Flamengo) which is not the "high end" area of Rio but a beatiful beach nontheless. We were also 3 blocks from the Metro station. In spite of the crazy traffic of cars and people during the busy Carnaval week we were able to get to all the places we wanted to.
Please note that Carnaval season in Rio is outrageously expensive- possibly a bubble. I am not sure the prices of everything are sustainable. I hope this is not a case of the familiar greed that will kill the golden goose.