@Ursula144
As I understood, in the USA is common to have the top sheet and then a duvet on top of it.
In Europe, we use a duvet inside the cover. So the bottom side of the cover work as a top sheet and the top of the cover protects the duvet in case someone sits on the bed.
So there is no need to have both- a duvet cover and a top sheet, it would be like 2 top sheets and would double your laundry cost.
Although it's a pain to put a duvet inside a cover, it is still easier than to wash a duvet after every guest.
You may put in the closet an additional thin blanket or cotton made a decorative cover in case your guests feel hot or cold under the duvet (we have ikea indira) and then wash it if used (it is rarely used)