Hi im interested in your Porsche Boxster
Hi. I'm happy to hear you're interested in my listing. Do you have any questions? My asking price is $15000
I was wondering if you would maybe do a trade in for a slight price reduction? I've got a Charger that's worth around 7,000 dollars. I'd like to trade that plus 10,500 dollars cash if possible.
Do you have cash in hand and does the charger have a clear title? 
The title is completely clear. No accidents ever on the vehicle. Good condition. Cash is in hand!
Well that works for me. We have a deal.