I want to find out if this is a real buyer or a scammer. He sent a check for a lot of money and expects me to send the difference to Austin, TX of the item I have for sale.

Advisory:
You may have been exposed to a variation of scam #1 , as described here:
http://phonehelp.2truth.com/facts.html

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Please reply to this post, to let us know you read it, or have taken suitable actions to protect yourself.

It's a scam! DO NOT attempt to cash his check!