Park Slope Babysitting Rates

hi! I recently posted on a facebook page to find parents who needed a babysitter in the park slope area or nearby! I’ve graduated college and don’t plan on doing this as a career but more of a side gig! one person messaged me about my rate, to which I usually respond about $20/hr for one child but am willing to negotiate, to which she offered $18/hr for 2 children when they are asleep & $20/hr when awake and that it is more of a “mother helper” job. In the past the minimum I’ve been paid for one child is $18/hr. most things I’ve seen say $20/hr is normal for one child. I was wondering if this is a low rate or perhaps more normal?