A song mixed

I have 2 dry voice tracks (Male - Female) and a karaoke track. Wanted to know if you can mix it with the best effects and how much you will charge for this. This is still in progress but I can send you the files for a demo now, and let me know, if you can send me a demo mix for say 15/20 secs. If we like it, we will order for the complete song , once we are done. (Early next week)