All rights reserved. First let me dispel all the myths. Your local bank can't do a quarter of what a mortgage broker can.
Banks have a specific amount of mortgage programs that have a set amount of parameters.
If you fall out of these parameters you don't get the mortgage. This is why so many people continue to rent, because their bank turned them down. Mortgage brokers are registered sales agents for many investors, hundreds of which you never heard of. Many are very specialized and some own local banks you have heard of, this gives brokers an edge over the local corner bank. And many mortgage brokers deal with your local bank, and may be able to get you approved with them even when they already turned you down.