Finding anything decent in Ipanema & Leblon for 1k/month is as likely as winning the lottery. Don't fool yourself.
For 1k you probably get somth with 30min walk to beach in Copa area (if you are lucky!). The main reason locals can afford to live there is because they own the hourse for generations and many people live together.
If you're up for adventures, you could try to live in Vidigal. Not my type of thing, but its an original idea those favela hostels.
On Christmas, NYE and Carneval people rent out ****, literally **** **** places for $300 a night. NYE in rio and midnight on copa is worth any price though.
My advice (thats how i did it):
- airbnb to feel out prices for your level of luxury
- check out agencies. They take a 20-30% cut, but often deliver better quality than airbnb (usually airbnb is good, not in rio though) despite the fees
- make a longterm deal with the owner (get rid of agency) so that NYE and Carneval is included. Thats how my first 3 months looked like
- Get to know somebody local and people that are well connected will find you something rly good. (got lucky there for a couple of months)
- make sure you have GOOD aircon until the end of april. You will thank me for it
- do it now