I see your confusion. If you have the proof of the the items mentioned below, they're in a way convertible to immediate cash. Specially bullet #1. Bullet # is still cash on hand. So when they say property, it's still a property which could be immediately converted to cash when you arrive and if the officer can verify that, it's a legit proof.
- documents that show property or capital payable to you, such as:
- stocks
- bonds
- debentures
- treasury bills
- documents that guarantee payment of a set amount of money, which are payable to you, such as:
- banker's drafts
- cheques
- travellers’ cheques
- money orders)