I stayed in Marcelo's apartment in Leblon while I studied Portuguese for 7 weeks in Rio. During that time, I was constantly pleased to look out the window and see the sea, take a short walk to the local shops and restaurants, or walk for <5 minutes down to the beach. The apartment is fully furnished with everything you need. The apartment is located on the border of the best two neighborhoods in Rio, and is truly walking distance from (almost) anything you could possibly want to do.
Marcelo, the owner, is responsive, helpful, and honest. He was very accommodating in every aspect of the process.
The prices are high, but they are more than fair for the market where the apartment is based and the neighborhood is far safer and "cooler" than copacabana, where prices go down. If you can, stay here for a wonderful vacation. Plus