@John Martin I manage properties here in Denver and struggle with the same issue. I list my properties on VRBO/Homeaway, Booking.com, and Tripadvisor/Flipkey. Airbnb is the only platform that offers the co-hosting feature. A property manager will have to add your apartment to their account, or you can give them your username and password so they can monitor the bookings and bill you for their PM fee. I personally list all of my properties on my VRBO account and pay my clients at the end of every month. This shouldn't be a big deal since most decent property managers will be using a "channel manager" that allows them to set pricing and communicate across multiple platforms via cloud based software.
If you're local to your property and want to save some money, Evolve Vacation Rental management offers an online-only management plan for 10% of gross revenue, and there are many other PMs, myself included, that offer a communication-only plan for around 5%. This can be a good option for owners willing to deal with minor repairs and the occasional guest issue that requires an in-person visit. Hope this helps!
Best,
Tyler