Maaser: In a case where money is being earned to pay off a debt, is this money subject to Maaser? For example $100 earned to pay off $1000 debt, or a tax refund that will be used to pay off debt.
If you need the money to pay off the debt, there is no obligation to give maaser from the income.
However, if you can live comfortably with your income, and pay of the debt with part of it, then the regular halachos of maaser will apply.
Please see here at length.