Let's estimate $25 per hour base. That is high for this area, but not high for four young kids for this area.
$25*40 = $1,000
$25*1.5*10= $375
Weekly total for 50 hours = $1,375
Let's estimate 10% additional on top for taxes.
$1,375 + 0.1*1,375 = $1,512.50
You will generally pay this amount for all 52 weeks per year. So annual amount:
$1,512.5*52 = $78,650
So, the total cost for your nanny will likely be around $79k. Most nannies get two weeks of paid vacation. Often the nanny gets to choose her weeks, so you may need to factor in additional money for backup care then if you do not plan to schedule your own vacations around the nanny's vacations. Some employers offer a health insurance stipend of $100-$200 per month, but that is not super common.
If you are not in a very walkable area, then you will also need to provide a car. In that case, you need to factor in the extra cost of insuring your nanny. That can depend on a ton of factors, but I would maybe ballpark an extra $100 per month.
And, as a previous poster noted, it would be best for your twins if they all get out of the house every day. Over summer, they can go to the park and many free activities, but you may want to factor in some money for activities in the colder months. Whether you consider that a nanny cost is up to you.
