You're a US citizen? I have done my applications in person but I have never had to show a hotel reservation or proof of funds. I haven't done Cameroon but my experience with other African countries is they aren't too worried about these for Americans. (I have had to show flight reservations for several countries)

A visa service would know exactly what info you really need, but the cheap route would be to do the bogus reservation, as suggested, if you don't want to take any chances.