How big of a downpayment?
You want as small of a mortgage as possible right? This then means, the biggest down payment as possible. Keeping in mind, to set aside money for all of the fees associated with buying a home. We can't forget about moving, repairs, renovations and possibly furniture.
The Home Buyer's Plan
If your a first time homebuyer with money in an RRSP, you can withdraw up to $25,000 without paying any income tax. If your spouse is eligible, that would be $50,000. Ask your Realtor how to best take advantage of this plan.
Lock into an interest rate? For how long?
This is a tough question. What if you "lock in" for five years and the rate goes into a period of decline? That could mean you are stuck paying more than you had to for a long time. But, if rates were to steadily climb over the next five years, locking in for five years now would be a great move. Your Realtor may have advise for you.
This information has been taken from howrealtorshelp.ca