Building application for a basement with holiday apartment and double garage above

Hello forum,

I am currently planning an extension to my detached house in Hessen (village location, very rural).
It is a basement (on a slope - only two sides are underground) and a double garage above it.
I have already taken care of sufficient parking spaces.

Now I want to know whether I should indicate the use as a holiday apartment directly or apply for a change of use later.
Are there special requirements that differ from normal, private living space?
Is there anything I should pay attention to regarding the whole holiday apartment issue?

Thanks in advance for your input! :)

I somehow can't quite follow you. So you want to build an apartment (Wohnkeller) in the hangar and the double garage above it? If the apartment is intended to be used exclusively as a holiday apartment from the beginning, I would have it approved as such right away. Otherwise, it doesn't make sense to get approval for a normal apartment now and then apply for the change of use to a holiday apartment.

Yes, exactly, used directly for business purposes as a holiday apartment. Do you know what you particularly have to pay attention to with a holiday apartment compared to regular living space?