CS is based on income. While some judges will just look at a paycheck stub, statutorally, income will be ones gross income (all sources of income) which is the same as what one declares on their federal income tax return which after calculations will give one their presumptive child support obligation.
If you wish to deviate from the states presumptive guidline child support, The court will need to make written findings as to the reasons for the deviation, including how the best interest of the child will be served by deviating from the Presumptive Amount of Child Support.
Forget about fair, right or just. Best interest is the only guiding factor and any deviation is strictly up to the judge.
You really won't find a better guide to Georgia child support and how to fill out the worksheet than
http://www.georgiacourts.org/csc/CompanionGuide_V2.pdfWHich states:
Statutory Reference for Findings of Facts: When ordering a deviation from the presumptive amount of child support, the
court or the jury shall consider all available income of the parents and shall make written findings or special interrogatory findings
that an amount of child support other than the amount calculated is reasonably necessary to provide for the needs of the child for
whom child support is being determined. The order or special interrogatory shall state: (i) The reasons for the deviation from the
presumptive amount of child support; (ii)The amount of child support that would have been required by law if the presumptive
amount of child support had not been rebutted; and (iii), How in its determination: (I) Application of the presumptive amount of
child support would be unjust or inappropriate; and (II) The best interest of the child for whom support is being determined will be
served by deviation from the presumptive amount of child support. O.C.G.A §19-6-15(i)(1)(B). See also O.C.G.A. §19-6-159c)(2)(E).
If the court does not include the finding of fact on why deviation from guideline fulfills the above guidelines, it will be overturned on appeal. Meaning, the judge isn't going to bother with trying to conclude why any deviation is in the best interest of the child except in the most egregious of cases.
If you want to try and attribute her husband paying her mortgage payment as income-----good frackin luck.
Really!