Defiantly a scam.

The way it work:
Guy wants to buy, sends you a cashiers check/money order for more than what you want for the item.
Tells you he will send "his shipping agency" to get the item.
Tells you to cash the check and wire transfer the "agency" the extra money to cover the shipping, this "agency" however is fake. It is really the scammer.
The check will turn out to be counterfeit and will bounce after some time.
You get stuck with the bounce check charges and because you wired some of the money to the scammer, you are out that cash.
Also, because you did cash/deposit a counterfeit check, you may be prosecuted criminally.

This is a money laundering scheme.

Always have a bank check to see if the cashiers check or money order is real.
Turn over any/all fake checks and correspondence to the bank, your local law enforcement, or your closest US Secret Service field office.


See:
http://www.fraudaid.com/solution_center/menu.htm
http://www.secretservice.gov/field_offices.shtml

Received messages from someone wanting to buy an item I had listed online. Offered to pay with a cashiers check and have a "Shipping Company Agent" come to my home to pick up my item. When I texted back that I only accepted  cash I never got another response.

Be aware. A person not wanting to pay in cash is most likely a scam.