This person has negative trust that is ~4 months old. Why exactly would you be willing to send first to someone like that? 
Because the first deal,he first pay.So I trust him.
But the second deal,I first ,then he get the btc and lost.
This is the common strategy most of the scammers will try to follow and scam people. First they do some small transaction with very honest and polite replies and will complete the trade very professional and when they get opportunity to cheat for bigger amount then they will make use of it. It will be costly learning for you, sorry about that.
