What is the best way to sync hotel reservations with Airbnb and Booking.com?

Hi, has anyone worked on making a hotel booking page? How did you sync reservations through pages like Airbnb or Booking.com? Did you use a PMS or Channel Manager? Or did you use an internal tool? I have a client who needs the page, but I don’t know what to tell them. Should I tell them to go buy a PMS or Channel Manager, and I’ll connect my page to it, or should I tell them I’ll make a web service to sync the platforms?