Are taxes being withheld or is the under the table? Gotta factor that in.
Pay him what you feel he deserves and if he sucks, fire the kid.
I would pay my babysitters 6$ p/hr (that was 6 years ago) to basically housesit while my kids were sleeping and I was at work. I ALWAYS paid my baby-sitters/nannies very well. When I was dating a man that told me to hire a nanny, she made more cash money than I did when I was at my stinking job. 'Course I wasn't the one paying her, but I did decide what her wage would be.