The first place most people think of when they think "mortgage" is "bank".
Bank mortgages generally require the purchaser to have a quite reasonable credit history and reliable income. Of all mortgage lenders they are likely to have the most rigorous requirements for credit history. However, banks are also likely to be the most stable organization with which to get your mortgage.
For that stability, you can pay a price. Banks may not give you the best interest rate on your mortgage. It's extremely important to shop around. The best thing to do is get pre-approved with a number of banks and other financial lenders. Then you can negotiate more effectively with them for the best possible rate.
Don't be intimidated just because you are dealing with a bank for your mortgage. What you need to remember is that you are doing them a favour. If the banks don't loan out money then the banks don't make money. Since the bank mortgage lender is going to make money from your business, you should treat the negotiation of your mortgage the same way you would anything you buy: