If you receive Support and/or Alimony, the amounts are generally included in your total income to determine the mortgage that you qualify for. You will need to show that the amount of this payment has been regularly received. Showing your last three months receipts will usually suffice. This may vary from lender to lender. A copy of your separation agreement or divorce decree is usually requested. If none exists then you will typically be asked to sign a declaration that says you have no outstanding liabilities remaining from your separation.
If you pay Child Support and/or Alimony, the amount paid out is deducted from your total income before determining the mortgage that you qualify for.