I'm a little confused by your facts. If you are paying half of the mortgage, is that where you live or where the kids live?
Generally, you will subtract the amount of support you pay for the two from your income (after FICA and NYC taxes), then calculate 17% of that amount for the third child. You can also determine what the child needs or what she wants and try to settle that way. You might want to get the agreement in writing and make sure you are paying by check or in some way that you have proof. Good luck.
Answered on Feb 23rd, 2014 at 4:11 PM