Vocal mastering

Hi, I'm after an estimate for someone to professionally master and mix vocals for a number of pop songs I've written. I would send you the vocals as a WAV file, as well as the backing track, and I'd need you to master the vocals (EQ, add compression, delay etc.) and then mix it with the backing track, to produce a more polished song. Ideally would like to try one and see how the results sound before committing to a few more.