The minimum down payment required is 5% of the purchase price of the home. And in order to avoid paying mortgage default insurance, you need to have at least a 20% down payment.
Your credit score plays a big part in the interest rate for which you will qualify, as the riskier you appear as a borrower, the higher your rate will be. Rate is definitely not the most important aspect of a mortgage, however, as many rock-bottom rates often come from no frills mortgage products. In other words, even if you qualify for the lowest rate, you often have to give up other things such as prepayments and porting privileges when opting for the lowest-rate product.