That part is fairly easy. Sign up for the One User free option on ERPNext.com. Go through your setup in setting up your company.
Now, let’s look at Customer A that wants to buy that ticket from Istanbul (If you are based in Istanbul, stay safe!!) to Paris. You buy the ticket on Amadeus and pay for it by Credit Card. Then you Invoice your customer for Cost of the Ticket + Your Commission.
Here’s what you do:
Set Up Amadeus as a Supplier (Home>Buying>Supplier) Take the most appropriate choices.
Account the ticket you just bought. You have to setup an Item on ERPNext to be able to do this.
To account for the ticket you just bought, you go to Accounts - Purchase Invoice and make a purchase invoice for Amadeus. Save and Submit. Add as much information as necessary in the Item Description.
Click on Make and Payment and make this payment. Since you paid by Credit Card, you have to Set Up an Account with the Mode of Payment Credit Card. You may want to add the transaction ID on Amadeus as reference on your purchase invoice. Save and Submit the document.
Now set up John Smith as a customer. You bill John for the ticket amount and the commission. You may need to setup a few things depending on whether you want to show on the invoice the Base Ticket Price and the Commission.
Depending on Accounting Principles applicable in your country, your Base Ticket price may or may not be treated as Income, You can set this up on ERPNext through the Income Account options. I have set up the Base Ticket Price as Indirect Income in my test system and the Commission on Sales as Direct Income.
Now you receive your payment from John. Most likely Credit Card. YOu set up another Credit Card Account, called Credit Card Receipts and tag an appropriate account to it. Again you may want to include the reference number of ticket on Amadeus for your accounting purposes.
Save and Submit the Payment Document. Now you have completed one cycle.
There is of course the details of making payment to your Credit Card account for the ticket you bought on Amadeus and receiving the amount that your customer paid for the ticket from your Credit Card receipt account to your Bank Account.
Other than the previous paragraph, I have simulated all the transactions on my test ERPNext system and here is the link to the Trial Balance, P&L and Balance Sheet extracts from ERPNext:
Please check these and if you think it is acceptable, I urge you to sign up on ERPNext.com and try it out for your self.
Happy to help you overcome any challenges you may encounter.
Hope you find ERPNext appropriate and will adopt ERPNext.