The embassy in Dakar is VERY strict about having a good I-864 (affidavit of support).
Make sure you are ready to show good income or assets. As long as they know that you can support them, atleast until you can get to the u.s. and they can begin working, you should be ok.
Consulate / USCIS Member Review #4141
Review on March 27, 2009:
