Applying for a subprime mortgage starts with gathering all of your financial documentation. You will need to show ID, proof of address, information pertaining to the property being mortgaged (valuation, purchase details, etc.). You'll be asked to provide financial statements indicating your assets and liabilities, previous tax returns to show income history, and paystubs or other proof of employment. Once you have gathered all of your information, you must complete an application form and submit to the lender for approval.