For VRBO, I was their earlier member so I pay the membership which is about $1500 a year per property. You have access to all the customer's contact information, you can email them, call them. I got a lot of bookings by talking to my customers by phone.
The later VRBO is not taking membership anymore. You can list your property there for free, but they charge by commission, I think it is about 15%. But for the commission based property, you don't have customer's contact information. You have to go through VRBO portal to communicate with your customers unless you got bookings first. You cannot call or talk to the customer over the phone from the commission based properties.
I don't have time to write more detail I am too busy to write more. There are more to talk about. When I have time, I will write some more to share.
There are other websites, like booking.com, flipkey, bedandbreakfast are all based on the commission listings.