If his case is in Illinois....
(1) The Court shall determine the minimum amount of
support by using the following guidelines:
Number of Children Percent of Supporting Party's
Net Income
1 20%
2 28%
3 32%
4 40%
5 45%
6 or more 50%
(2) The above guidelines shall be applied in each
case unless the court makes a finding that application of the guidelines would be inappropriate, after considering the best interests of the child in light of evidence including but not limited to one or more of the following relevant factors:
(a) the financial resources and needs of the
child;
(b) the financial resources and needs of the
custodial parent;
(c) the standard of living the child would have
enjoyed had the marriage not been dissolved;
(d) the physical and emotional condition of the
child, and his educational needs; and
(e) the financial resources and needs of the
non‑custodial parent.
If the court deviates from the guidelines, the
court's finding shall state the amount of support that would have been required under the guidelines, if determinable. The court shall include the reason or reasons for the variance from the guidelines.
(3) "Net income" is defined as the total of all
income from all sources, minus the following deductions:
(a) Federal income tax (properly calculated
withholding or estimated payments);
(b) State income tax (properly calculated
withholding or estimated payments);
(c) Social Security (FICA payments);
(d) Mandatory retirement contributions required
by law or as a condition of employment;
(e) Union dues;
(f) Dependent and individual
health/hospitalization insurance premiums;
(g) Prior obligations of support or maintenance
actually paid pursuant to a court order;
(h) Expenditures for repayment of debts that
represent reasonable and necessary expenses for the production of income, medical expenditures necessary to preserve life or health, reasonable expenditures for the benefit of the child and the other parent, exclusive of gifts. The court shall reduce net income in determining the minimum amount of support to be ordered only for the period that such payments are due and shall enter an order containing provisions for its self‑executing modification upon termination of such payment period.