As soon as they mention an agent its a sure scam. If they give you a phone number type it into google and see what comes up. I had one a while ago where he was texting, so I knew he had his phone with him, so I called, he didn't answer, but then he texted said he couldn't speak was at work. Put his number into google and up it came on scam alert sites.
But in any case don't trust anyone that wants to pay by paypal. 2 reasons.
1. Fake credit card scam. They set up an account with a stolen card, paypal figures it out days later and reverses the transaction. Money and car gone.
2. Cars are supposedly exempt from buyer protection but there are plenty of cases online where people have accepted paypal payments from people who turned up and took the car, and were then hit with a claim through buyer protection from people claiming the car was not as described, or broke down and paypal reverses all or part of the transaction.
Anyone wanting to pay by paypal in full or in part is doing it for their benefit, not yours.
You will probably also get the low ballers with messages like hey mate if your car doesn't sell after a few weeks give me a call. More common on ebay but same type of time wasters.
Good luck with sale. Will be a good indication of the value of a matching numbers car.