Escrow is fine when there are terms to be met, and you do want to show good faith. But for $500, when you could be out substantially more because of the return shipping, I'd not go for it.
If the seller wants to see the good faith, put the money in escrow, but fly down to see it. Don't let it be shipped.
I used escrow once to pay my rent, when the landlord had not completed repairs. In Maryland, you can be evicted if you don't pay, even if the place isn't safe to live. But you can pay into escrow, and only let they money be released upon the meeting of your terms.
