Hello
Hi how are you? 
Good. I am in the market for a new bike. Is this one in good shape?
This one is in fantastic shape! It's got some great options too. It has a step thu frame, cantilever brakes and a shimano drivetrain. 
That sounds awesome. How much do you want for it?
I'm asking $350 for it, but I'm willing to negotiate, especially for cash.
Would you be willing to lower the price down to 250? I will pick it up myself.
Sorry, 250 is too low. I'll deliver it myself for $300, and we have a deal.