Pre-qualification starts the loan process. Once a lender has gathered information about a borrower's income and debts, a determination can be made as to how much the borrower can pay for a house; the ability to repay the mortgage is verified by your current employment and total income.
An Agreement in Principle (AIP), also known as Approval in Principle, Decision in Principle, Mortgage in Principle, or a Mortgage Promise, is a written estimate from a lender stating what you might be able to borrow. You can usually get an AIP within 24 hours and it is normally valid for up to 90 days.
When your offer has been accepted you will meet with your financial advisor to complete the mortgage application. Once all the paperwork has been approved, the mortgage company will direct the survey to go ahead. After the survey provides you with your valuation, you should receive your mortgage offer.