My question involves a consumer law issue in the State of: Georgia
I am a private party in the state of Georgia. On Saturday a buyer came to see my car and agreed to purchase it for $15,500, contingent on a wheel bearing repair and a satisfactory PPI (pre-purchase inspection). I asked for a non-refundable deposit and he wrote a personal check for it. He was in a hurry to leave, but I insisted we have a written document of some kind and created a purchase agreement that states:
"I (my name) accept a non-refundable deposit of $500 towards (vehicle) at a purchase price of $15,500 pending nothing major showing on a PPI. This is inclusive of the front wheel bearing repair. to be made by seller. Also pending clean car fax. Minus $150 for the rear tires, making the final price $15,350.
(my signature, printed name, date)
(his signature)
this agreement expires July 7-24-13 if a formal agreement can be agreed"
We wrote it as we talked as he was in a hurry as he was running late for something. I realized there was no expiration so I asked him to write in it expires Wednesday, so he wrote that in below the signatures. I'm not sure what it means, except that there seem to be two explanations. The reasonable one being that a formal agreement made by Wednesday supercedes this agreement, and the unreasonable one being that I will hold the car for him until the end of time.
Either way, I offered to let him take the car. Since I needed to have the repair done immediately, I am unfamiliar with the local shops and would need time to research them, and I was happy with the sale price, I agreed to let him have it repaired at the Toyota dealership near his house. It made sense to us as it would be convenient for him, as he told me he wanted to take it there for a PPI. He left the car there Monday morning and they repaired the wheel bearing, which cost me almost $700. I could have done it myself for far less ($150 I think) or had a smaller shop do it for considerably less.
Tuesday he picks the car up, declines the PPI at Toyota that he is supposed to pay for, and tells me he needs to talk to his wife. Later that day he calls me and lets me know that they do not want to purchase the car. In the conversation he explains he had his cousin at Firestone do a PPI, and the only things they found were a scratch on the front bumper, a loose mudguard, and a barely audible ticking from the HVAC fan. Seeing as this was nothing new nor major wrong, I asked why they don't want to buy it, and he told me they simply wanted to purchase a new car.
I met with him to receive the vehicle, and he demanded his check be returned to him. I refused to return it as our agreement states it is non-refundable. Also because I have told other buyers that the car is sold and they have gone elsewhere or moved on. We got into an argument about it where he began to pretend it was refundable if he did not buy the car and he continued to refuse to give me the deposit we had agreed upon. I received the receipt for the over-priced repair and left. He put a stop payment on the check he gave me.
Now I am out $700 for a repair I made based on a purchase agreement we had. I would have made the repair for far less on my own time. I am also out my other buyers who have moved on and out my non-refundable deposit of $500. He is saying that the deposit is towards the purchase and because he did not purchase the car, the document is now "void." Sounds like BS to me. What are my options here?
TL;DR
I took a non-refundable deposit contingent on a $700 repair and successful PPI.
I had the vehicle repaired and the buyer refused a PPI. He had a PPI done by his cousin informally.
He then changed his mind and returned the vehicle, saying he wanted to purchase a new car instead.
He put a stop payment on the deposit check and is telling me he does not have to pay me.

