A Buyer's Agent; is an agent hired by buyers to help them find and negotiate the purchase of a home. This agent works for the best interests of the buyers, not the sellers. On most transactions, there is usually a listing agent and a selling agent. The selling agent is sometimes referred to as the buyer's agent, because s/he works on the buyer's behalf and it easier than explaining each time that the "selling agent" is not the listing agent and is actually the buyer's agent.
The sale of the severed portion of vacant land would not be subject to GST/HST since it is not capital property used primarily (more than 50%) in a business and it is not being sold in the course of a business. However, if the land was subdivided into more than two parts, sales of the severed portions are not exempt unless the portion is sold to a relative (or to a former spouse or common-law partner) for their personal use.