A B-lender or alternative lender takes on more risk than a bank does, so it charges for that risk through a higher rate and often a lender fee, and the overall cost of borrowing over the life of the mortgage increases meaningfully compared with a standard insured loan.
Down payment does some of the work a credit score would otherwise do. Below the federal minimum of 5 percent up to $500,000 and 10 percent on the amount above that, a lender has less room to work with, so a larger down payment can offset a weaker score in some cases.
A mortgage broker who works with alternative lenders can tell you quickly what is actually realistic for your file. Get your hand-reviewed valuation from Joel Dyck.