Many home buyers search for a home they want, then apply for a mortgage and hope for the best. A better approach is to find out how much mortgage you can qualify for, then look at homes that you know are within your price range.
You will probably save time, aggravation and money by having your lender tell you the size of mortgage you qualify for and the likelihood that you will be approved. Pre-qualification may also give you added bargaining power with the seller if he knows there will be no delays in closing the deal.