A pre-approved mortgage provides an interest rate guarantee from a lender for a specified period of time (usually 60 to 90 days) and for a set amount of money. The pre-approval is calculated based on information provided by you and is generally subject to certain conditions being met before the mortgage is finalized. Conditions would usually be things like 'written employment and income confirmation' and 'downpayment from your own resources', for example. A pre-approved mortgage is one of the first steps a homebuyer should take before beginning the buying process.