It depends what part of nova. I would say a legal resident, full and fluent English (your child will be learning to speak eventually from this person), will provide transportation (your car, if her car reimburse at the government rate of .51 cents a mile), will take to classes, story times ect as becomes appropriate, addresses all mess and dishes that are made during her time at work, child's laundry (wash/fold/put away) and truly treats your son like her own child while she is there.
So all that, 1 baby, $18/hr +2 weeks vacation (one her choice, one yours), 5 sick days, all normal holidays.
Oh, and this rate also requires a minimum of 5 years nanny experience
And for sake of true disclosure, I am a nanny in N. Arlington 15 years experience, do all the things above and more. I do make more then is but I watch a family of 5... Luckily the older ones are very independent
Good luck with your search and I hope you find the right nanny for you!