No, it is not a common RV rental business practice to leave your luggage with the RV rental office. RV rental offices will generally avoid doing this for liability and hasslels involved should anything go wrong with the luggage.
If you have your personal car or a rental car then you could likely park at the RV rental location.
However if you are an international flyer and have neither a car nor any other place then you may consider following options:
RVShare or Outdoorsy – The RV Owners are regular folks and with some persuasion may be open for you to leave your luggage in their garage for the duration of your trip.
Hotels – Look for a good quality hotel and book a night at the beginning or end of your RV rental trip and then work with them to hold your luggage for the duration of your RV rental trip.