Often, because of their high cost, home buyers tend not to replace the existing doors. Not always, in fact, it is necessary to replace them. If it is a period house, with original doors dating back to earlier stages of construction or restoration, then they should leave, otherwise you can embellish the existing gates, they present no peculiarities to be preserved.
A little imagination and the use of an artisan or a decorator is the recommended way. Remember also that by replacing the handle and the metal components of a door provides an effect of extraordinary novelty. Least expensive (although I am sure of quality handles expensive) than what would be required to buy a new door, you renew the face of this essential functional component.