This can come from a variety of sources, including RRSP's. To start the process, once you have your downpayment your bank representative can 'pre-approve' you for a mortgage based on your credit history and earning power. You will also discover how much money the banks will lend you, and then know what price range of home to look at. These are bank staff who only with the bank's with mortgage applicants, from all of that bank's branches. Because they only deal mortgages, they are more knowledgable than the branch staff.
Some people like to shop around, rather than stay with their bank for the mortgage.
In these cases an independent mortgage broker can review your situation and find the best lender and lowest rate possible for your situation. We have an excellent independent mortgage broker who works in our office. She can also arrange a first and second mortgage as an alternative to CMHC financing if you don't quite meet their rules. We have found from experience that it is best to have a broker working through us, for you. This way they are accountable to us and you.