Child support does not affect taxes. Ever. Even if a judge rules that what a person can claim on taxes is affected by child support, that part of the judge's ruling is invalid.
If you only make "around" $7000 per year and no one else can claim you as a dependent, then your federal income is $0.
Your "earned" income is simply the amount that you make at work. Neither the child support nor the house payments affect this. If you itemize, which there is no reason for you to do, then the house payments would affect taxable income, but not earned income. If you do not itemize (which, again, is unnecessary), then they affect neither earned income nor taxable income.