Someone may tell me that s/he wants the house, but reluctant to pay a deposit. I would say that until I see the deposit, I would not promise anything and the house is still open.
I have seen so many people saying that they absolutely want the house, but they "change" their mind later.
"So, if you want the house, you pay the deposit, otherwise, you are welcome to come back to see if it is still available. Whoever pays the deposit first will have the priority.