Once you've found a house you like and have the financial resources to buy it, you must decide how much to offer. In putting together your actual offer, consider the following factors:
Treat this as only a rough estimate of what the seller would like to receive, and recognize that different sellers price houses very differently. Some sellers deliberately overprice, others ask for pretty close to what they hope to get and a few (often the cleverest) under-price their houses in the hope that potential buyers will compete and overbid.
What you can pay for a house will probably depend on how much you already have in cash and how much you can reasonably borrow in a mortgage. When figuring out the cost of the house, be sure to factor in your share of the closing costs, which will be about 2%-5% of the purchase price.
This is the most important factor, as you do not wish to offer and land up paying more for the property then what it is worth. Here one does a comparative market analysis, and if you don't know how to do one of those, don't worry that is what you have a realtor for.
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.