We are a start-up Online Travel Agent and would like to ask how to receive commissions from the hotel.

Our business model takes so-called “Agency Model” in which guest pay the accommodation fee to the hotel and the hotels pay the OTA commission after the guests’ stay have taken place.
Since our website itself doesn't have a payment system, the guests will make their payments directly at the hotel.

In the situation above, what could be the payment method for us to receive commissions from the hotels?
Please give us any possible payment methods.
Major worldwide hotel chains seem to use the payment systems such as Onyx and TACS.

We are aiming for approaching both major hotel chains and small local hotels.
If the payment methods change depending on the scale of the hotels, we would like to know the difference as well. (especially, the payment methods for small hotels)

Appreciate your cooperation.