New properties(or what is considered new) carry an advantage of being able to deduct interest as an expense before working out the profit payable on the profit from rent. Also there is a different treatment for how long the properties are held before tax is potentially not payable on any profit from the sale.
An old property can be considered depending on the extent of renovations which leads to a CCC or a new Kitchen.
If a new investment property is sold before five years of ownership, tax will be payable on the profit. For an old property this time period in ten years. However new properties are considered new for 20 years, meaning the next owner can still carry some of the tax treatment.
This advice is based on the rules in the year of 2022, it is always best to get tailormade accounting advice from a reputable accountant.