Unless you signed the purchase and sales agreement before June 18, 2009, all new housing/ substantively renovated home with the ownership or possession transferred on or after July 1, 2010 will be subject to HST.
And, the relevant cost such as real estate agent commission, legal service, and home inspection will be subject to HST effective July 1, 2010.
However, if you purchase the house as primary residence, you can receive a rebate at 75% of provincial component of HST, WITH maximum rebate at $24k. This means that there will be no impact on new home purchase with price up to 400k as 2% PST is included in the prices of new homes currently sold.