Hi Kayandoro1,
I recommend you, to come first to Cotonou and then look around, what is available. There are many different sort of residencies, usually starting @ about 400'000 FCFA for a house with garden.
You may find apartments from 150'000 FCFA up always per month. Usually they ask for a deposit of at least three month!
You can find any information about Benin on the site
http://@#$%&.biz/information/
Kind regards
Heiner