There are management companies and services you can reach out to and use for basic management of the property between bookings. As for the keys and providing access to rental for guests, I'd highly reccommend getting a good keypad digital lock.
I love this new lock we recently got! It syncs with your AirBNB calendar so each time a guest books a stay with you, it automatically sends them an email confirmation with their key code. It auto updates itself and auto switches codes for you when guests check in and check out! Saves me a whole world of time and makes hosting not only super easy on me, but easy and convenient for our guests!
Here's a link to it for you to check out:
https://www.amazon.com/AirLocking-Smart-Lock-for-AirBNB/dp/B0759NPC5Y/ref=as_sl_pc_tf_til?tag=airloc...