website that takes payment keeping a percentage as a finders fee

I think you have enough examples and are capable of using google as the rest of us.  You could also look to ebay, any of the crowd funding sites like kickstarter etc.

Take a look at their terms of service.

As example, airbnb's is below.  You should see something similar on the other sites that do the same.  If you are going to do this on your own, the first thing you need to do is get a merchant account.  Make sure the gateway they use as a good api for your own programming.  There are many, http://www.authorize.net/ is just one.  Not all have the same type of api's but similar.  http://developer.authorize.net/  

The work flow is for you to charge the customer $xx and you will want to make it clear the credit card charge will be from rgb192 company.   Then you will in turn payout a percentage of the fee you collect to the company offering the service.

When you get a merchant account, you need to disclose what you are doing with the account and they will base the discount fees you pay based on the risk of the type of business and your own credit.  What you need to take into consideration are your own terms with people purchasing on the site and the service providers.  Think about things like refunds and customer placing a stop with their credit card company.   Let's say a customer uses the service provided, for whatever reason, they go back to their credit card company and deny the charge, there is a charge back fee you need to pay plus the funds being taken away from  you.   The key is to get all your ducks lined up for every possible scenario.


Excerpt of airbnb's TOS:
The fees displayed in each Listing are comprised of the Accommodation Fees (defined below) and the Guest Fees (defined below.) Where applicable, Taxes may be charged in addition to the Accommodation Fees and Guest Fees. The Accommodation Fees, the Guest Fees and applicable Taxes are collectively referred to in these Terms as the “Total Fees”. The amounts due and payable by a Guest solely relating to a Host’s Accommodation are the “Accommodation Fees”. Please note that it is the Host and not Airbnb which determines the Accommodation Fees. The Accommodation Fee may include a cleaning fee, at the Host’s discretion.

Airbnb charges a fee to Guests based upon a percentage of applicable Accommodation Fees which are the “Guest Fees”. The Guest Fees are added to the Accommodation Fees to calculate the Total Fees (which will also include applicable Taxes) displayed in the applicable Listing. Airbnb will collect the Total Fees at the time of booking confirmation (i.e. when the Host confirms the booking within 24 hours of the booking request) and will initiate payment of the Accommodation Fees (less Airbnb’s Host Fees (defined below)) to the Host within 24 hours of when the Guest arrives at the applicable Accommodation (except to the extent that a refund is due to the Guest).

Appointment of Airbnb as Payment Agent for Host
Each Host hereby appoints Airbnb as the Host’s limited agent solely for the purpose of collecting payments made by Guests on behalf of the Host. Each Host agrees that payment made by a Guest to Airbnb shall be considered the same as a payment made directly to the Host and the Host will make the Accommodation available to Guest in the agreed upon manner as if the Host has received the Accommodation Fees. Each Host agrees that, Airbnb may, in accordance with the cancellation policy selected by the Host and reflected in the relevant Listing, (i) permit the Guest to cancel the booking and (ii) refund to the Guest that portion of the Accommodation Fees specified in the applicable cancellation policy. In accepting appointment as the limited authorized agent of the Host, Airbnb assumes no liability for any acts or omissions of the Host.

Please note that Airbnb does not currently charge fees for the creation of Listings. However, you acknowledge and agree that Airbnb reserves the right, in its sole discretion, to charge you for and collect fees from you for the creation of Listings. Please note that Airbnb will provide notice of any Listing fee collection via the Site, Application and Services, prior to implementing such a Listing fee feature

thanks for explanation of this type of website.