Sales tax is not payable on real estate sales, only on the commission.
If a developer takes a piece of land and builds condos or villas he will have to charge 10% GST to the buyer of each new home. If a speculator buys a beat up old house and completely re-models it he will have to charge the new GST if he sells it right away. If a hotel owner decides "enough" of tourism and wants to sell he will have to charge 10% GST because it's considered a non-established residential property sale.
Or am I reading the new law wrong? I hope so.