I would advise valuing each property by direct market comparison. Basically, you need to analyse recent sales evidence with the objective of finding the most comparable property rather than the average of several sales (although that might have to suffice).
You can chose whatever units you like, for comparisons sake:
- per square metre of land area
- per square metre of gross building area
- per square meter of net lettable area etc…
Its important to segment the market by locality and factors such as building type and quality, land area and so on…
Once the sales are analysed, you need to adjust for differences such as quality and land area. Allowances also need to be made for timing, i.e. to correct sales to a standard date, particularly if the market is rising or falling in your area at a substantial rate.
Additionally, particular circumstances of a sale might affect the outcome here. For example, adjust for purchases by an adjoining owner (they might be willing to pay a higher price than they should’ve), the vendor being a mortgagee or other anxious seller (the price might be understated), etc…
Keep in mind that the confidential nature of property transactions makes it difficult to obtain all of the sales details you require and reconcile which prices are outliers. You might be able to purchase reports that detail sales evidence in certain suburbs, and consult various estate agents.
This type of valuation is very easy – you can do it yourself and don’t require expert assistance. What you want to find out, at the end of the day, is how much the properties you are looking to purchase are ACTUALLY worth, not what you are being told by interested parties or what the prices being asked are. Obviously, you’re going to look for something reasonably or under-priced, once that is done.
Hope that helps