Most real estate is usually sold via the "open market" using conventional estate agents or live property auctions. However, there is a growing trend of properties being sold outside the traditional norm known as "off-market property" where the vendor and purchaser deal more directly or via a third party broker albeit at a much lower fee than conventional agents fees. 

This method of sale lends itself to sellers who have a property which they perhaps don't want made public, whether that be for private or commercial purposes. Many landlords see it as much viable option especially when it is being sold with a "sitting-tenant" as this means less stress and upheaval for the tenant. It also tends to attract a much more pragmatic buyer who is well versed in refurbishing property and may not necessarily require a mortgage to purchase it.