I have seen in my travels everything from $200 to reserve the property and the balance on check in to everything being due at booking and is non-refundable. I personally think it is a bit unreasonable but these are the owners terms. I don't know where the property is located but the fact that you booking 8 months in advance and it's over a major holiday, I can see how he is coming up with these terms.
I guess you have 2 choices:
1. Pay the amount and purchase trip insurance OR
2. Wait to book the property within the 6 month period you stated regarding your credit card.