If the property is sold while your tenancy continues, your deposit should be transferred to the new landlord, and you should not normally have to pay a second deposit. The sale itself does not automatically end your tenancy or remove your existing rights, including the applicable notice rules. Ask the outgoing landlord and purchaser for written confirmation that the deposit and tenancy records have been transferred, and keep your payment evidence. When the tenancy ends, the landlord holding the deposit may propose deductions for valid reasons, but any disagreement can ultimately be decided through the RTB dispute resolution process.