Note: You need to have enough money to purchase the property regularly. Go up to a the sign that allows you to purchase a property. Press right on the D-Pad and that will take you to the confirm purchase prompt. Press right on the D-Pad again to confirm your purchase and immediately after doing so, pause the game. Now replay any mission in the replay mission menu (preferably a short one) and finish the mission. When the game loads you back in the overworld, the property you purchased should be owned by you but you will still have all of your money.