The main purposes of a down payment is to ensure that the lending institution has enough capital to create money for a loan in fractional reserve banking systems and to recover some of the balance due on the loan in the event that the borrower defaults.
If the borrower is unable to pay off the loan in its entirety, the down payment amount is forfeited.
State or local housing authorities, a non-profit organization, or lender usually set the requirements and conditions for the DPA program.
Some programs require you or your loan officer to take a short course on Down Payment Assistance for first time home buyers.
Some states have special programs supporting home purchases in selected geographic areas.