Le's say I want to buy a property to rent. If it is already being rented out I will need to verify the actual rents being paid recently as I won't be able to charge more than 4% above these levels. I will always be vulnerable to my new tenant making a claim that I was overcharging them and that the rent was actually lower. If a decent Landlord has not been charging full market rents... If I want to buy this, I will pay a lot less than I would pay for a property which has not been let in the last two years. Or, I could buy it and keep it empty until the two years have elapsed Certain rental properties within a Rent Pressure Zone will be exempt – (a) those that are new to the rental market (i.e. they have not been rented at any time in the last two years), and Maybe sellers should keep their properties empty if they are trying to sell them A property which has not been let in the last two years will be worth more than a property which has been let. So if it has been empty, maybe keep it empty before selling it.