OK - you want to buy a house and you need to take out a mortgage. What next?
First of all, find a good, local mortgage specialist who can give you some different options - your real estate professional can give you some recommendations. You may have choices on length of term, principal and interest, interest only - there are a number of different options/combinations.
This is some of the paperwork you will need to provide for your mortgage pre-approval (which means the lender will check your credit unlike a pre-qualification which, frankly, is pretty worthless and which means that the lender has not checked your credit.) The list is by no means exhaustive:
Pay stubs, tax returns (probably going back 2-3 years), 1099's for the self-employed, evidence of any additional income, proof of funds for the down payment, HUD closing statements for any other property purchased within the last 2-3 years, executed lease(s) if applicable on other property, proof of property tax and insurance payments, information on any legal proceedings in process etc.
You may be able to get a written pre-approval, subject to providing the paperwork, as above. If so, you are ready to make your offer!