Hi,
Opening an account in Benin is not that hard. Some banks will open a Personal Savings Account for you once you produce your international passport as well as you country's embassy card (issued by your country's embassy in Cotonou).
Some, however would request that you also bring the 'Carte de Sejour'. This is the resident permit issued by the Immigration Service in Cotonou.
I particularly like the Banque Atlantique, but, There are other equally good banks: Ecobank, UBA, Diamond, SGB, Orabank, Bank of Africa (BAOA).
This is hoping this Information is of some help.
Cheers!
Afroking231