We are going to assume that your credit card is linked to your "Trading Account"
Enter you own company up as a Creditor (Then you can use this for other things as well), enter the trading account bank account number in the Bank Account area (Right click of Creditor)
Make the payment method direct.
Go to Transactions - Invoice Creditor - Pick up the Property address and the Creditor is your commany.
Enter the total amount of the purchase (GST inclusive) - ensure that you note in the comments that (Your company name) is being reimbursed for a purchase (name it) made for the property.
This has moved the money from the property and put it against the Creditor - When you are ready you can do a Payment Creditor as normal and upload the file to the bank to pay your Trading Account. (You have now been reimbursed)
It is a good idea to scan your receipt for the purchase and attached it to the property diary. Remember to add a diary group if you want it to go out with your statements.
So in Summary
The owner has been charged for the complete GST purchase
Your company will receive a maintenance fee plus GST (only if you charge a maintenance fee)
The owner has not been charged GST twice for the purchase itselft. He has been charged GST for the purchase itself (included in cost) and then for your maintenance fee. This is normal.