Can i use a diffrent icing instead of buttercream under fondant?

Im making my brothers birthday cake for sunday, and its my first fondant cake. im going with homemade marshmellow fondant, and i know your supposed to put buttercream icing on the cake before the fondant, but what if i put plain vanilla betty crocker whipped icing instead because the fondant is already costly to make and its to much trouble to make the butter cream, anyone help?:$