I'm purchasing an aircraft from a seller in Florida. I emailed the seller a week ago an offer, the seller replied in email accepting the offer. As part of the offer I wired $4500 down payment. The seller has since wanted to back out of the deal, presumably so he can sell the aircraft to another buyer for more money. Assuming he does this and returns my deposit, what legal course do I have? The price we agreed upon was very good and it would be about $20,000 more to buy another aircraft like it.